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Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2018	Feb. 12, 2019	Jun. 30, 2018
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY
Trading Symbol	MNOV
Entity Registrant Name	MEDICINOVA INC
Entity Central Index Key	0001226616
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		42,171,810
Entity Public Float			$ 314,684,033

Consolidated Balance Sheets - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 62,313,418	$ 27,991,743
Prepaid expense and other current assets	444,942	336,580
Total current assets	62,758,360	28,328,323
Goodwill	9,600,240	9,600,240
In-process research and development	4,800,000	4,800,000
Investment in joint venture		616,657
Property and equipment, net	53,134	62,886
Other long-term assets	10,958	10,958
Total assets	77,222,692	43,419,064
Current liabilities:
Accounts payable	616,753	1,520,225
Accrued liabilities	1,575,161	1,360,744
Total current liabilities	2,191,914	2,880,969
Long-term deferred rent and lease liability	27,211
Deferred tax liability	201,792	201,792
Long-term deferred revenue	1,694,163	1,694,163
Total liabilities	4,115,080	4,776,924
Commitments and contingencies
Stockholders’ equity:
Common stock, $0.001 par value; 100,000,000 shares authorized at December 31, 2018 and December 31, 2017; 42,081,306 and 36,452,893 shares issued and outstanding at December 31, 2018 and December 31, 2017, respectively	42,081	36,453
Additional paid-in capital	429,289,968	380,156,510
Accumulated other comprehensive loss	(93,150)	(94,623)
Accumulated deficit	(356,131,287)	(341,456,200)
Total stockholders’ equity	73,107,612	38,642,140
Total liabilities and stockholders’ equity	$ 77,222,692	$ 43,419,064

Consolidated Statements of Operations and Comprehensive Loss - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating expenses:
Research, development and patents	$ 5,625,814	$ 4,223,746	$ 3,519,172
General and administrative	9,961,012	8,803,347	7,362,662
Total operating expenses	15,586,826	13,027,093	10,881,834
Operating loss	(15,586,826)	(13,027,093)	(10,881,834)
Other expense, net	(22,894)	(25,601)	(47,038)
Interest income	939,909	145,508	66,647
Loss before income taxes	(14,669,811)	(12,907,186)	(10,862,225)
Income tax benefit (expense)	(5,276)	1,744,050	(3,754)
Net loss applicable to common stockholders	$ (14,675,087)	$ (11,163,136)	$ (10,865,979)
Basic and diluted net loss per common share	$ (0.36)	$ (0.32)	$ (0.33)
Shares used to compute basic and diluted net loss per share	41,124,909	35,137,028	32,986,740
Net loss applicable to common stockholders	$ (14,675,087)	$ (11,163,136)	$ (10,865,979)
Other comprehensive income, net of tax:
Foreign currency translation adjustments	1,473	1,377	6,765
Comprehensive loss	$ (14,673,614)	$ (11,161,759)	$ (10,859,214)

Consolidated Statements of Stockholders' Equity - USD ($)	Total	Preferred stock	Common stock	Additional paid-in capital	Accumulated other comprehensive income (loss)	Accumulated deficit
Balance at Dec. 31, 2015	$ 32,752,974	$ 2,200	$ 29,957	$ 352,250,667	$ (102,765)	$ (319,427,085)
Balance, shares at Dec. 31, 2015		220,000	29,956,495
Share-based compensation	3,972,533			3,972,533
Issuance of shares under an employee stock purchase plan	87,729		$ 27	87,702
Issuance of shares under an employee stock purchase plan, shares			26,650
Issuance of common stock under at-the-market equity distribution and sales agreements, net of offering costs	159,529		$ 36	159,493
Issuance of common stock under at-the-market equity distribution and sales agreements, net of offering costs, shares			36,248
Conversion of preferred stock to common stock		$ (2,200)	$ 2,200
Conversion of preferred stock to common stock, shares		(220,000)	2,200,000
Issuance of common stock for option exercises	$ 829,526		$ 173	829,353
Issuance of common stock for option exercises, shares	172,585		172,585
Exercise of warrants	$ 7,588,852		$ 2,132	7,586,720
Exercise of warrants, shares			2,131,700
Net loss	(10,865,979)					(10,865,979)
Foreign currency translation adjustments	6,765				6,765
Balance at Dec. 31, 2016	34,531,929		$ 34,525	364,886,468	(96,000)	(330,293,064)
Balance, shares at Dec. 31, 2016			34,523,678
Share-based compensation	4,474,945			4,474,945
Issuance of shares under an employee stock purchase plan	77,319		$ 15	77,304
Issuance of shares under an employee stock purchase plan, shares			15,153
Issuance of common stock under at-the-market equity distribution and sales agreements, net of offering costs	9,891,315		$ 1,689	9,889,626
Issuance of common stock under at-the-market equity distribution and sales agreements, net of offering costs, shares			1,689,436
Issuance of common stock for option exercises	$ 426,013		$ 105	425,908
Issuance of common stock for option exercises, shares	105,579		105,579
Exercise of warrants	$ 402,378		$ 119	402,259
Exercise of warrants, shares			119,047
Net loss	(11,163,136)					(11,163,136)
Foreign currency translation adjustments	1,377				1,377
Balance at Dec. 31, 2017	38,642,140		$ 36,453	380,156,510	(94,623)	(341,456,200)
Balance, shares at Dec. 31, 2017			36,452,893
Share-based compensation	6,330,305			6,330,305
Issuance of shares under an employee stock purchase plan	$ 51,009		$ 7	51,002
Issuance of shares under an employee stock purchase plan, shares	7,094		7,094
Issuance of common stock under public offering, net of offering costs	$ 38,472,971		$ 4,546	38,468,425
Issuance of common stock under public offering, net of offering costs, shares			4,545,928
Issuance of common stock under at-the-market equity distribution and sales agreements, net of offering costs	1,515,105		$ 200	1,514,905
Issuance of common stock under at-the-market equity distribution and sales agreements, net of offering costs, shares			200,000
Issuance of common stock for option exercises	$ 407,196		$ 125	407,071
Issuance of common stock for option exercises, shares	125,391		125,391
Exercise of warrants	$ 2,362,500		$ 750	2,361,750
Exercise of warrants, shares			750,000
Net loss	(14,675,087)					(14,675,087)
Foreign currency translation adjustments	1,473				1,473
Balance at Dec. 31, 2018	$ 73,107,612		$ 42,081	$ 429,289,968	$ (93,150)	$ (356,131,287)
Balance, shares at Dec. 31, 2018			42,081,306

Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
Consolidated Statements of Cash Flows - USD ($)	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating activities:
Net loss	$ (14,675,087)	$ (11,163,136)	$ (10,865,979)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Non-cash share-based compensation	6,330,305	4,474,945	3,972,533
Depreciation and amortization	25,881	28,098	14,127
Tax benefit from fluctuations in other comprehensive income			(1,901)
Change in joint venture investment	(19,867)	1,673	32,139
Changes in assets and liabilities:
Receivables, prepaid expenses and other assets	(111,682)	242,064	175,495
Accounts payable, accrued liabilities and other current liabilities	(663,671)	1,246,630	127,373
Deferred tax liability, deferred revenue and other long-term liabilities		(1,754,208)
Net cash used in operating activities	(9,114,121)	(6,923,934)	(6,546,213)
Investing activities:
Proceeds from dissolution of joint venture	636,524
Acquisitions of property and equipment	(10,200)		(84,483)
Net cash provided by (used) in investing activities	626,324		(84,483)
Financing activities:
Proceeds from issuance of common stock, exercise of common stock options and warrants, net of issuance costs	42,757,772	10,719,707	8,577,907
Proceeds from issuance of equity under ESPP	51,009	77,319	87,729
Net cash provided by financing activities	42,808,781	10,797,026	8,665,636
Effects of foreign exchange rates on cash	691	614	6,348
Net increase in cash and cash equivalents	34,321,675	3,873,706	2,041,288
Cash and cash equivalents, beginning of period	27,991,743	24,118,037	22,076,749
Cash and cash equivalents, end of period	62,313,418	27,991,743	24,118,037
Supplemental disclosure of cash flow information:
Income taxes paid	$ 6,005	$ 9,203	$ 6,035

Organization and Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2018

Accounting Policies [Abstract]

Organization and Summary of Significant Accounting Policies

1. Organization and Summary of Significant Accounting Policies

Organization and Business

The Company was incorporated in the state of Delaware in September 2000 and is a public company. The Company’s common stock is listed in both the United States and Japan and trades on the NASDAQ Global Market and the JASDAQ Market of the Tokyo Stock Exchange. The Company is a biopharmaceutical company focused on developing novel, small molecule therapeutics for the treatment of serious diseases with unmet medical needs with a commercial focus on the United States market. The Company’s current strategy is to focus its development activities on MN-166 (ibudilast) for neurological disorders such as progressive multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS), chemotherapy-induced peripheral neuropathy, degenerative cervical myelopathy, glioblastoma, and substance dependence and addiction (e.g., methamphetamine dependence, opioid dependence, and alcohol dependence), and MN-001 (tipelukast) for fibrotic diseases such as nonalcoholic steatohepatitis (NASH) and idiopathic pulmonary fibrosis (IPF). The Company’s pipeline also includes MN-221 (bedoradrine) for the treatment of acute exacerbation of asthma and MN-029 (denibulin) for solid tumor cancers.

As of December 31, 2018, the Company had available cash and cash equivalents of $62.3 million and working capital of $60.6 million.

Principles of Consolidation

The consolidated financial statements include the accounts of MediciNova, Inc. and its wholly-owned subsidiaries. All intercompany transactions and balances are eliminated in consolidation.

Segment Reporting

The Company operates in a single operating segment – the acquisition and development of small molecule therapeutics for the treatment of serious diseases with unmet medical needs.

Use of Estimates

The accompanying consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (“GAAP”). The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. Actual results could differ from those estimates.

Cash and Cash Equivalents

Cash and cash equivalents consist of cash and other highly liquid investments with original maturities of three months or less from the date of purchase. Cash equivalents at December 31, 2018 and 2017 consisted of money market funds.

Concentrations and Credit Risk

The Company maintains cash balances at various financial institutions and such balances commonly exceed the $250,000 amount insured by the Federal Deposit Insurance Corporation. The Company also maintains money market funds at various financial institutions which are not federally insured although are invested primarily in U.S. government securities. The Company has not experienced any losses in such accounts and management believes that the Company does not have significant credit risk with respect to such cash and cash equivalents.

Fair Value of Financial Instruments

Financial instruments, including cash and cash equivalents, prepaid expenses and other current assets, accounts payable and accrued liabilities, are carried at cost, which management believes approximates fair value because of the short-term maturity of these instruments.

Goodwill and Purchased Intangibles

The Company records goodwill and other intangible assets based on the fair value of the assets acquired. In determining the fair value of the assets acquired, the Company utilizes extensive accounting estimates and judgments to allocate the purchase price to the fair value of the net tangible and intangible assets acquired. The Company uses the discounted cash flow method to estimate the value of intangible assets acquired.

The Company assesses goodwill and indefinite lived intangible assets for impairment using fair value measurement techniques on an annual basis during the fourth quarter of the year, or more frequently if indicators of impairment exist. The impairment evaluation is performed assuming that the Company operates in a single operating segment and reporting unit. When impaired, the carrying value of goodwill is written down to fair value. The goodwill impairment test involves consideration of qualitative information to determine if it is more likely than not that the fair value of a reporting unit is less than its carrying value. If such a determination is made, then the traditional two-step goodwill impairment test is applied. The first step, identifying a potential impairment, compares the fair value of a reporting unit with its carrying amount, including goodwill. If the carrying value of the reporting unit exceeds its fair value, the second step would need to be conducted; otherwise, no further steps are necessary as no potential impairment exists. The second step, measuring the impairment loss, compares the implied fair value of the reporting unit goodwill with the carrying amount of that goodwill. Any excess of the reporting unit goodwill carrying value over the respective implied fair value is recognized as an impairment loss. There was no impairment of goodwill for all periods presented.

The Company periodically re-evaluates the original assumptions and rationale utilized in the establishment of the carrying value and estimated lives of its long-lived assets. The criteria used for these evaluations include management’s estimate of the asset’s continuing ability to generate income from operations and positive cash flows in future periods as well as the strategic significance of any intangible assets in the Company’s business objectives. If assets are considered to be impaired, the impairment recognized is the amount by which the carrying value of the assets exceeds the fair value of the assets. There was no impairment of long-lived assets for the periods presented.

Research, Development and Patents

Research and development costs are expensed in the period incurred. Research and development costs primarily consist of salaries and related expenses for personnel, facilities and depreciation, research and development supplies, licenses and outside services. Such research and development costs totaled $5.3 million, $3.9 million and $3.1 million for the years ended December 31, 2018, 2017 and 2016, respectively.

Costs related to filing and pursuing patent applications are expensed as incurred, as recoverability of such expenditures is uncertain. The Company includes all external costs related to the filing of patents on developments in Research, Development and Patents expenses. Such patent-related expenses totaled $0.3 million for the years ended December 31, 2018 and 2017 and $0.4 million for the year ended December 31, 2016.

Share-Based Compensation

The Company estimates the fair value of stock options using the Black-Scholes option pricing model on the date of grant. The fair value of equity instruments expected to vest are recognized and amortized on a straight-line basis over the requisite service period of the award, which is generally three to four years; however, the Company’s equity compensation plans provide for any vesting schedule as the board may deem appropriate. Forfeitures are recognized as they occur.

Net Loss Per Share

The Company computes basic net loss per share using the weighted average number of common shares outstanding during the period. Diluted net income per share is based upon the weighted average number of common shares and potentially dilutive securities (common share equivalents) outstanding during the period. Common share equivalents outstanding, determined using the treasury stock method, are comprised of shares that may be issued under the Company’s stock option agreements and warrants. Common share equivalents were excluded from the diluted net loss per share calculation because of their anti-dilutive effect for all periods presented.

Potentially dilutive outstanding securities excluded from diluted net loss per common share because of their anti-dilutive effect for the periods presented are as follows:

	December 31,
	2018		2017		2016
Stock options		6,609,647		5,514,038		4,432,017
Warrants		—		750,000		1,067,067
Total		6,609,647		6,264,038		5,499,084

Recent Accounting Pronouncements

In May 2017, the FASB issued ASU No. 2017-09, Compensation-Stock Compensation Topic 718-Scope of Modification Accounting ("ASU 2017-09"). This guidance will clarify when changes to the terms and conditions of share-based payment awards must be accounted for as modifications. Entities will apply the modification accounting guidance if the value, vesting conditions, or classification of an award changes. ASU 2017-09 is effective for the Company at the beginning of fiscal 2018, including interim periods within fiscal 2018. Early adoption is permitted and the guidance will be applied prospectively to awards modified on or after adoption. The Company adopted this standard in 2018 and there was no significant impact on the Company’s consolidated financial statements at the time of adoption.

In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2014-09, Revenue from Contracts with Customers. ASU 2014-09 and its related amendments provide companies with a single model for accounting for revenue arising from contracts with customers and supersedes prior revenue recognition guidance, including industry-specific revenue guidance. The core principle of the model is to recognize revenue when control of the goods or services transfers to the customer, as opposed to recognizing revenue when the risks and rewards transfer to the customer under the existing revenue guidance. The guidance permits companies to either apply the requirements retrospectively to all prior periods presented, or apply the requirements in the year of adoption, through a cumulative adjustment. The Company adopted the new accounting standard using the modified retrospective transition method effective January 1, 2018 and there was no impact to the Company’s historical Kissei contract. See Note 2 for further information.

In February 2016, the FASB issued ASU 2016-02, Leases, which introduces the recognition of lease assets and lease liabilities by lessees for those leases classified as operating leases under previous guidance. The new standard establishes a right-of-use (ROU) model that requires a lessee to record an ROU asset and a lease liability on the balance sheet for all leases with terms longer than 12 months. The new standard is effective for fiscal years beginning after December 15, 2018 and interim periods within those fiscal years with early adoption permitted. The Company has completed its identification of leases which is comprised of two building leases and copiers. The Company is in the process of quantifying the impact to the balance sheet while the impact to the statement of operations is expected to be immaterial. The Company will adopt the new accounting standard using a modified retrospective transition option effective January 1, 2019.

In January 2017, the FASB issued ASU No. 2017-04, Intangibles - Goodwill and Other, which eliminates step two of the quantitative goodwill impairment test. Step two required determination of the implied fair value of a reporting unit, and then a comparison of this implied fair value with the carrying amount of goodwill for the reporting unit, in order to determine any goodwill impairment. Under the new guidance, an entity is only required to complete a one-step quantitative test, by comparing the fair value of a reporting unit with its carrying amount, and any goodwill impairment charge is determined by the amount by which the carrying amount exceeds the reporting unit’s fair value. However, the loss should not exceed the total amount of goodwill allocated to the reporting unit. The standard is effective for the Company in the first quarter of 2020, with early adoption permitted as of January 1, 2017, and is to be applied on a prospective basis. The Company early adopted this standard with its December 31, 2018 impairment test. The Company’s annual impairment test was completed using a qualitative approach, so the early adoption did not impact the results of the Company’s impairment test.

In August 2018, the FASB ASU No. 2018-13, Fair Value Measurement (Topic 820), which eliminates, adds and modifies certain disclosure requirements for fair value measurements. The modified standard eliminates the requirement to disclose changes in unrealized gains and losses included in earnings for recurring Level 3 fair value measurements and requires that changes in unrealized gains and losses be included in other comprehensive income for recurring Level 3 fair value measurements of instruments. The standard also requires the disclosure of the range and weighted average used to develop significant unobservable inputs and how weighted average is calculate for recurring and nonrecurring Level 3 fair value measurements. The amendment is effective for fiscal years beginning after December 15, 2019 and interim periods within that fiscal year with early adoption permitted. The Company does not expect the standard to have a material impact on its consolidated financial statements.

Balance Sheet Details

12 Months Ended

Dec. 31, 2018

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Balance Sheet Details

4. Balance Sheet Details

Property and Equipment

Property and equipment, net, consist of the following:

	December 31,
	2018			2017
Leasehold improvements	$	16,121		$	15,742
Furniture and equipment		235,095			233,441
Software		285,446			285,418
		536,662			534,601
Less accumulated depreciation and amortization		(483,528	)		(471,715	)
Property and equipment, net	$	53,134		$	62,886

The Company uses the straight-line method to record depreciation expense with useful lives of three to five years. Depreciation and amortization of property and equipment of $25,881, $28,098, and $14,127, was recorded for the years ended December 31, 2018, 2017 and 2016, respectively.

Accrued Liabilities

Accrued liabilities consist of the following:

	December 31,
	2018		2017
Accrued compensation	$	1,137,869	$	952,470
Research and development costs		226,597		122,665
Professional services fees		18,763		144,105
Other		191,932		141,504
Total accrued liabilities	$	1,575,161	$	1,360,744

Commitments and Contingencies

12 Months Ended

Dec. 31, 2018

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

5. Commitments and Contingencies

Lease Commitments

The Company subleases its office space under an operating lease with an initial term of four years and one month, expiring in December 2021. Rent expense for the years ended December 31, 2018, 2017 and 2016 was $229,613, $254,593 and $256,314, respectively. The difference between the minimum lease payments and the straight-line amount of total rent expense is recorded as deferred rent. Deferred rent at December 31, 2018 and 2017 was $24,762 and $253, respectively.

As of December 31, 2018, the total estimated future annual minimum lease payments under the Company’s non-cancelable building and copier leases for the years ending after December 31, 2018 are as follows:

Years ending December 31:
2019	$	182,847
2020		144,234
2021		149,951
2022		1,532
2023		1,404
Total minimum payments	$	479,968

Product Liability

The Company’s business exposes it to liability risks from its potential drug products. A successful product liability claim or series of claims brought against the Company could result in the payment of significant amounts of money and divert management’s attention from running the business. The Company may not be able to maintain insurance on acceptable terms, or the insurance may not provide adequate protection in the case of a product liability claim. To the extent that product liability insurance, if available, does not cover potential claims, the Company would be required to self-insure the risks associated with such claims. The Company believes it carries reasonably adequate insurance for product liability.

License and Research Agreements

The Company has entered into in-licensing agreements with various pharmaceutical companies. Under the terms of these agreements, the Company has received licenses to research, know-how and technology claimed, in certain patents or patent applications. Under these license agreements, the Company is generally required to make upfront payments and additional payments upon the achievement of milestones and/or royalties on future sales of products until the later of the expiration of the applicable patent or the applicable last date of market exclusivity after the first commercial sale, on a country-by-country basis.

No amounts have been expended under these agreements during the years ended December 31, 2018, 2017 or 2016. For products currently in development, future potential milestone payments based on product development of MN-166 (ibudilast) and MN-001 (tipelukast) are $10.0 million as of December 31, 2018. For all other products, future potential milestone payments related to development milestones and commercialization milestones totaled $33.5 million as of December 31, 2018. There are no minimum royalties required under any of the license agreements. The Company is unable to estimate with certainty the timing on when these milestone payments will occur as these payments are dependent upon the progress of the Company’s product development programs.

Legal Proceedings

From time to time, the Company may be subject to legal proceedings and claims in the ordinary course of business. The Company is not aware of any such proceedings or claims that it believes will have, individually or in aggregate, a material adverse effect on its business, financial condition or results of operations.

Share-based Compensation

12 Months Ended

Dec. 31, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Share-based Compensation

7. Share-based Compensation

Stock Incentive Plans

In June 2013, the Company adopted the 2013 Equity Incentive Plan, or 2013 Plan, under which the Company may grant stock options, stock appreciation rights, restricted stock, restricted stock units and other awards to individuals who are then employees, officers, non-employee directors or consultants of the Company or its subsidiaries. The 2013 Plan is the successor to the Company’s Amended and Restated 2004 Stock Incentive Plan, or 2004 Plan. A total of 2,500,000 shares of common stock were initially reserved for issuance under the 2013 Plan. At the annual meeting of stockholders held in June 2018, the Company’s stockholders approved an amendment to the 2013 Plan to increase the number of shares of common stock reserved for issuance under the plan by 1,500,000 shares. In addition, “returning shares” that may become available from time to time are added back to the plan. “Returning shares” are shares that are subject to outstanding awards granted under the 2004 Plan that expire or terminate prior to exercise or settlement, are forfeited because of the failure to vest, are repurchased, or are withheld to satisfy tax withholding or purchase price obligations in connection with such awards. Although the Company no longer grants equity awards under the 2004 Plan, all outstanding stock awards granted under the 2004 Plan will continue to be subject to the terms and conditions as set forth in the agreements evidencing such stock awards and the terms of the 2004 Plan. As of December 31, 2018, 1,494,592 shares remain available for future grant under the 2013 Plan.

The Company issues employee performance-based stock options, the vesting of which is based on a determination made by the board of directors as to the achievement of certain corporate objectives at the end of the performance period. The grant date of such awards is the date on which the board of directors makes its determination. For periods preceding the grant date, the expense related to these awards is measured based on their fair value at each reporting date. As of December 31, 2018, total performance options outstanding and unvested was 1,162,000. These options became vested in 2019.

Stock Options

Options granted under the 2013 Plan and 2004 Plan have terms of ten years from the date of grant unless earlier terminated and generally vest over a three or four-year period.

The exercise price of all options granted during the years ended December 31, 2018, 2017 and 2016 was equal to the market value of the Company’s common stock on the date of grant.

A summary of stock option activity and related information for the years ended December 31, 2018, 2017 and 2016 is as follows:

	Number of Option Shares			Weighted Average Exercise Price
Outstanding at December 31, 2015		4,133,969			$	4.69
Granted		1,158,000			$	4.00
Exercised		(172,585	)		$	4.81
Cancelled		(687,367	)		$	11.27
Outstanding at December 31, 2016		4,432,017			$	3.47
Granted		1,195,000			$	6.10
Exercised		(105,579	)		$	4.04
Cancelled		(7,400	)		$	7.76
Outstanding at December 31, 2017		5,514,038			$	4.03
Granted		1,222,000			$	7.11
Exercised		(125,391	)		$	3.25
Cancelled		(1,000	)		$	4.52
Outstanding at December 31, 2018		6,609,647			$	4.61
Exercisable at December 31, 2018		5,408,814			$	4.07

	Number of Option Shares			Weighted Average Grant-Date Fair Value
Non-vested at December 31, 2017		1,261,837		$	3.73
Granted		1,222,000		$	4.57
Vested		(1,283,004	)	$	3.78
Non-vested at December 31, 2018		1,200,833		$	4.04

Cash received from stock option exercises for the years ended December 31, 2018, 2017 and 2016 was $407,196, $426,013 and $829,526, respectively. The aggregate intrinsic value of options exercised was $788,423, $198,164 and $414,572 for the years ended December 31, 2018, 2017 and 2016, respectively. Options outstanding and exercisable at December 31, 2018 had a weighted average contractual life of 6.32 years, respectively.

As of December 31, 2018 and 2017, the total intrinsic value of options outstanding was $23.6 million and $13.6 million, respectively. Total intrinsic value of options exercisable was $22.2 million and $12.9 million as of December 31, 2018 and 2017, respectively.

Employee Stock Purchase Plan

Under the Company’s 2007 Employee Stock Purchase Plan (ESPP), 300,000 shares of common stock were originally reserved for issuance. In addition, the shares reserved automatically increase each year by a number equal to the lesser of: (i) 15,000 shares; (ii) 1% of the outstanding shares of common stock on the last day of the immediately preceding fiscal year; or (iii) such lesser amount as determined by the Board. The ESPP permits full-time employees to purchase common stock through payroll deductions (which cannot exceed 15% of each employee’s compensation) at the lower of 85% of fair market value at the beginning of the offering period or the end of each six-month offering period. The ESPP is considered a compensatory plan and the Company records compensation expense.

For the year ended December 31, 2018, an aggregate of 7,094 shares were issued under the ESPP, leaving 191,878 shares available for future issuance.

Compensation Expense

The estimated fair value of each stock option award was determined on the date of grant using the Black-Scholes option valuation model with the following weighted-average assumptions for stock option grants:

	Year Ended December 31,
	2018			2017			2016
Stock Options
Risk-free interest rate		2.52	%		2.06	%		1.60	%
Expected volatility of common stock		61.56	%		72.55	%		78.30	%
Dividend yield		0.00	%		0.00	%		0.00	%
Expected option term (in years)		4.56			5.67			5.57

The estimated fair value of employee stock purchase rights under the Company’s ESPP was determined on the date of grant using the Black-Scholes option valuation model with the following weighted-average assumptions for stock option grants:

	Year Ended December 31,
	2018			2017			2016
Employee Stock Purchase Plan
Risk-free interest rate		2.07	%		1.09	%		0.44	%
Expected volatility of common stock		70.41	%		38.34	%		51.65	%
Dividend yield		0.00	%		0.00	%		0.00	%
Expected option term (in years)		0.5			0.5			0.5

The risk-free interest rate assumption is based upon observed interest rates appropriate for the expected term of employee stock options. The expected volatility is based on the historical volatility of the Company’s common stock. The Company has not paid nor does the Company anticipate paying dividends on its common stock in the foreseeable future. The expected term of employee stock options is based on the simplified method as provided by the authoritative guidance on stock compensation, as the historical stock option exercise experience does not provide a reasonable basis to estimate the expected term.

The weighted-average fair value of each stock option granted during the years ended December 31, 2018, 2017 and 2016, estimated as of the grant date using the Black-Scholes option valuation model, was $4.57 per option, $3.78 per option and $2.64 per option, respectively.

Share-based compensation expense for stock option awards and ESPP shares are reflected in total operating expense for each respective year. For the years ended December 31, 2018, 2017 and 2016, share-based compensation expense related to stock options and the ESPP was $6.3 million, $4.5 million and $4.0 million, respectively, of which $4.5 million, $3.1 million and $2.9 million was recorded as a component of general and administrative expense, respectively, and $1.8 million, $1.4 million and $1.1 million was recorded as a component of research, development and patents expense, respectively.

As of December 31, 2018, there was $0.3 million of unamortized compensation cost related to unvested stock option awards which is expected to be recognized over a remaining weighted-average vesting period of 0.03 years, on a straight-line basis.

Stockholders' Equity

12 Months Ended

Dec. 31, 2018

Equity [Abstract]

Stockholders' Equity

8. Stockholders’ Equity

Equity Offerings

On May 22, 2015, the Company entered into an at-the-market issuance sales agreement (ATM Agreement) with MLV & Co. LLC (MLV), pursuant to which the Company may sell common stock through MLV from time to time up to an aggregate offering price of $30.0 million. Sales of the Company’s common stock through MLV, if any, can be made by any method that is deemed to be an “at-the-market” equity offering as defined in Rule 415 promulgated under the Securities Act of 1933, as amended, including sales made directly on NASDAQ, on any other existing trading market for the common stock or to or through a market maker. MLV may also sell the common stock in privately negotiated transactions, subject to the Company’s prior approval. The Company agreed to pay MLV an aggregate commission rate of up to 4.0% of the gross proceeds of any common stock sold under this agreement. Proceeds from sales of common stock will depend on the number of shares of common stock sold to MLV and the per share purchase price of each transaction. The Company is not obligated to make any sales of common stock under the sales agreement and may terminate the sales agreement at any time upon written notice. On September 16, 2016, the Company amended the original sales agreement with MLV to also include FBR Capital Markets & Co as a sales agent.

The following table summarizes the activity under the ATM agreements for the following periods (in thousands except share price and shares sold):

	Year Ended December 31,
	2018		2017		2016
Gross proceeds		1,562		10,303.0		264
Net proceeds		1,515		9,891.3		159.5
Shares sold		200,000		1,689,436		36,248
Price range	$7.81		$5.30 - 6.98		$6.90 - 7.54

Warrants

During the year ended December 31, 2018, 750,000 shares of the Company’s common stock were issued upon exercise of warrants for gross proceeds of $2.4 million. During the years ended December 31, 2017 and 2016, 119,047 and 2,131,700 shares of the Company’s common stock were issued upon exercise of warrants for gross proceeds of $0.4 million and $7.6 million, respectively, with warrants exercisable for 198,020 shares expiring unexercised on May 10, 2017.

At December 31, 2018, there were no warrants outstanding to purchase shares of the Company’s common stock.

Common Stock Reserved for Future Issuance

The following table summarizes common stock reserved for future issuance at December 31, 2018:

Common Stock reserved for issuance under the ESPP			191,878
Common stock reserved for issuance upon exercise of options outstanding (under the 2004 Plan and 2013 Plan)			6,609,647
Common stock reserved for future equity awards (under the 2013 Plan)			1,494,592
			8,296,117

Public Offering

On February 12, 2018, the Company completed a firm-commitment underwritten public offering of 4,419,890 shares of common stock at a purchase price of $9.05 per share for aggregate gross proceeds of $40.0 million and received aggregate net proceeds of approximately $37.4 million, net of underwriting discounts and commissions and offering expenses. Additionally, the Company granted the underwriters a 30-day option to purchase up to an additional 662,983 shares of common stock at the public offering price, and on February 21, 2018, the Company sold an additional 126,038 shares of Common Stock for gross proceeds of $1.1 million pursuant to the partial exercise by the underwriters of their over-allotment option.

Income Taxes

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Income Taxes

9. Income Taxes

A reconciliation of loss before income taxes for domestic and foreign locations for the years ended December 31, 2018, 2017 and 2016 is as follows:


	2018			2017			2016
United States	$	(14,689,617	)	$	(12,940,362	)	$	(10,892,276	)
Foreign		19,807			33,176			30,050
Loss before income taxes	$	(14,669,810	)	$	(12,907,186	)	$	(10,862,226	)

A reconciliation of income tax benefit (expense) for the years ended December 31, 2018, 2017 and 2016 is as follows:


Current:	2018			2017			2016
Federal	$	—		$	—		$	1,489
State		—			—			412
Foreign		(5,276	)		(10,158	)		(5,655	)
Total current income tax benefit (expense)		(5,276	)		(10,158	)		(3,754	)
Deferred:
Federal		—			1,329,888			—
State		—			424,320			—
Foreign		—			—			—
Total deferred income tax benefit (expense)		—			1,754,208			—
Total income tax benefit (expense)	$	(5,276	)	$	1,744,050		$	(3,754	)

The significant components of deferred income taxes at December 31, 2018 and 2017 are as follows (in thousands):


Deferred tax assets:	2018			2017
Net operating loss carryforwards	$	62,025		$	59,480
Capitalized licenses		286			429
Research tax credits		8,434			8,160
Stock options		3,922			2,585
Other, net		580			572
Total deferred tax assets		75,247			71,226
Deferred tax liabilities
In process R&D		(1,343	)		(1,343	)
Total deferred tax liabilities		(1,343	)		(1,343	)
Net deferred tax assets		73,904			69,883
Valuation allowance		(74,106	)		(70,085	)
Net deferred tax liability	$	(202	)	$	(202	)

The Company has established a valuation allowance against net deferred tax assets due to the uncertainty that such assets will be realized. The Company periodically evaluates the recoverability of the deferred tax assets. At such time as it is determined that it is more likely than not that deferred tax assets will be realizable, the valuation allowance will be reduced.

At December 31, 2018, the Company has federal and California net operating losses, or NOL, carryforwards of approximately $248.9 million and $139.6 million, respectively. The federal NOL carryforwards begin to expire in 2020, and the California NOL carryforwards begin to expire in 2028. At December 31, 2018, the Company also had federal and California research tax credit carryforwards of approximately $6.96 million and $1.9 million, respectively. The federal research tax credit carryforwards begin to expire in 2024, and the California research tax credit carryforward does not expire and can be carried forward indefinitely until utilized.

The above NOL carryforward and the research tax credit carryforwards are subject to an annual limitation under Section 382 and 383 of the Internal Revenue Code of 1986, and similar state provisions due to ownership change limitations that have occurred which will limit the amount of NOL and tax credit carryforwards that can be utilized to offset future taxable income and tax, respectively. In general, an ownership change, as defined by Section 382 and 383, results from transactions increasing ownership of certain stockholders or public groups in the stock of the corporation by more than 50 percentage points over a three-year period. The Company has not completed an IRC Section 382/383 analysis since 2011 regarding the limitation of net operating loss and research and development credit carryforwards. There is a risk that additional changes in ownership have occurred since the completion of the Company’s analysis, which was through December 2011. If a change in ownership were to have occurred, additional NOL and tax credit carryforwards could be eliminated or restricted. If eliminated, the related asset would be removed from the deferred tax asset schedule with a corresponding reduction in the valuation allowance. Due to the existence of the valuation allowance, limitations created by future ownership changes, if any, related to the Company’s operations in the United States will not impact the Company’s effective tax rate.

A reconciliation of the federal statutory income tax rate to the Company’s effective income tax rate is as follows:


	2018			2017			2016
Federal statutory income tax rate		21.0	%		35.0	%		35.0	%
State income taxes, net of federal benefit		6.4			5.2			3.5
Tax credits		1.5			1.1			0.9
Change in valuation allowance		(27.2	)		247.4			(8.4	)
Permanent differences		(0.1	)		(0.3	)		(0.1	)
Expiration of attributes		—			(18.7	)		(17.2	)
Tax Cuts and Jobs Act		—			(253.7	)		—
Stock compensation		(1.7	)		(2.9	)		(13.6	)
Other		0.1			0.4			(0.1	)
Provision for income taxes		0.0	%		13.5	%		0.0	%

On December 22, 2017, the Tax Cuts and Jobs Act of 2017 (TCJA) was signed into law making significant changes to the Internal Revenue Code, including, but are not limited to (a) reducing the federal corporate income tax rate from 35% to 21%, effective January 1, 2018; and (b) eliminating the federal corporate alternative minimum tax (AMT) and changing how existing AMT credits can be realized; and (c) eliminating several business deductions and credits, including deductions for certain executive compensation in excess of $1 million. As a result of the rate reduction, the company reduced the deferred tax asset balance as of December 31, 2017 by $32.7 million and the valuation allowance by $33.4 million.

In December 2017, the SEC issued Staff Accounting Bulletin No. 118 (SAB 118), which provides guidance on accounting for the income tax effects of the TCJA. SAB 118 provides a measurement period that should not extend beyond one year from the TCJA enactment date for companies to complete the accounting relating to the TCJA under Accounting Standards Codification Topic 740, “Income Taxes” (ASC 740). In accordance with SAB 118, a company must reflect the income tax effects of those aspects of the TCJA for which the accounting under ASC 740 is complete. To the extent that a company’s accounting for TCJA-related income tax effects is incomplete, but the company is able to determine a reasonable estimate, it must record a provisional estimate in its financial statements. If a company cannot determine a provisional estimate to be included in its financial statements, it should continue to apply ASC 740 on the basis of the provisions of the tax laws that were in effect immediately before the enactment of the TCJA. The Company has completed its evaluation of the potential impacts of IRC Section 162(m) as amended by the Act of 2017 prior to December 22, 2018 and there was no change to the Company’s previous analysis.

The Company files income tax returns in the United States, California and foreign jurisdictions. Due to the Company’s losses incurred, the Company is essentially subject to income tax examination by tax authorities from inception to date. The Company’s policy is to recognize interest expense and penalties related to income tax matters as tax expense. At December 31, 2018, there are no unrecognized tax benefits nor any significant accruals for interest related to unrecognized tax benefits or tax penalties.

Quarterly Financial Data

12 Months Ended

Dec. 31, 2018

Quarterly Financial Information Disclosure [Abstract]

Quarterly Financial Data

11. Quarterly Financial Data (Unaudited)

The following table presents certain quarterly financial data for eight consecutive quarters ended December 31, 2018 and 2017. The unaudited quarterly information has been prepared on the same basis as the audited consolidated financial statements and, in the opinion of management, includes all adjustments, necessary for a fair presentation of this data (in thousands, except per share data).

	Year Ended December 31, 2018
	1st Quarter			2nd Quarter			3rd Quarter			4th Quarter
Selected quarterly financial data:
Total operating expenses	$	4,667		$	3,400		$	7,028		$	492
Net loss		(4,543	)		(3,144	)		(6,780	)		(208	)
Net loss applicable to common stockholders		(4,543	)		(3,144	)		(6,780	)		(208	)
Basic and diluted net loss per common share (1)		(0.12	)		(0.08	)		(0.16	)		(0.00	)

	Year Ended December 31, 2017
	1st Quarter			2nd Quarter			3rd Quarter			4th Quarter
Selected quarterly financial data:
Total operating expenses	$	3,024		$	2,805		$	3,792		$	3,406
Net loss		(3,017	)		(2,789	)		(3,755	)		(1,602	)
Net loss applicable to common stockholders		(3,017	)		(2,789	)		(3,755	)		(1,602	)
Basic and diluted net loss per common share (1)		(0.09	)		(0.08	)		(0.11	)		(0.02	)

(1)	Net loss per share is computed independently for each of the quarters presented. Therefore, the sum of the quarterly net income and loss per share will not necessarily equal the annual per share calculation.

Organization and Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2018

Accounting Policies [Abstract]

Principles of Consolidation

The consolidated financial statements include the accounts of MediciNova, Inc. and its wholly-owned subsidiaries. All intercompany transactions and balances are eliminated in consolidation.

Segment Reporting

The Company operates in a single operating segment – the acquisition and development of small molecule therapeutics for the treatment of serious diseases with unmet medical needs.

Use of Estimates

Cash and Cash Equivalents

Concentrations and Credit Risk

Fair Value of Financial Instruments

Goodwill and Purchased Intangibles

Research, Development and Patents

Share-Based Compensation

Net Loss Per Share

Potentially dilutive outstanding securities excluded from diluted net loss per common share because of their anti-dilutive effect for the periods presented are as follows:

	December 31,
	2018		2017		2016
Stock options		6,609,647		5,514,038		4,432,017
Warrants		—		750,000		1,067,067
Total		6,609,647		6,264,038		5,499,084

Recent Accounting Pronouncements

Revenue Recognition Policy

Revenues consist mainly of research and development services performed under a contract with a customer. The Company evaluates the separate performance obligation(s) under each contract, allocates the transaction price to each performance obligation considering the estimated stand-alone selling prices of the services and recognizes revenue upon the satisfaction of such obligations over time or at a point in time dependent on the satisfaction of one of the following criteria: (1) the customer simultaneously receives and consumes the economic benefits provided by the vendor’s performance (2) the vendor creates or enhances an asset controlled by the customer (3) the vendor’s performance does not create an asset for which the vendor has an alternative use, and the vendor has an enforceable right to payment for performance completed to date.

Balance Sheet Details (Tables)

12 Months Ended

Dec. 31, 2018

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Property and Equipment Net

Property and equipment, net, consist of the following:

	December 31,
	2018			2017
Leasehold improvements	$	16,121		$	15,742
Furniture and equipment		235,095			233,441
Software		285,446			285,418
		536,662			534,601
Less accumulated depreciation and amortization		(483,528	)		(471,715	)
Property and equipment, net	$	53,134		$	62,886

Accrued Liabilities

Accrued liabilities consist of the following:

	December 31,
	2018		2017
Accrued compensation	$	1,137,869	$	952,470
Research and development costs		226,597		122,665
Professional services fees		18,763		144,105
Other		191,932		141,504
Total accrued liabilities	$	1,575,161	$	1,360,744

Share-based Compensation (Tables)

12 Months Ended

Dec. 31, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Stock Option Activity and Related Information

A summary of stock option activity and related information for the years ended December 31, 2018, 2017 and 2016 is as follows:

	Number of Option Shares			Weighted Average Exercise Price
Outstanding at December 31, 2015		4,133,969			$	4.69
Granted		1,158,000			$	4.00
Exercised		(172,585	)		$	4.81
Cancelled		(687,367	)		$	11.27
Outstanding at December 31, 2016		4,432,017			$	3.47
Granted		1,195,000			$	6.10
Exercised		(105,579	)		$	4.04
Cancelled		(7,400	)		$	7.76
Outstanding at December 31, 2017		5,514,038			$	4.03
Granted		1,222,000			$	7.11
Exercised		(125,391	)		$	3.25
Cancelled		(1,000	)		$	4.52
Outstanding at December 31, 2018		6,609,647			$	4.61
Exercisable at December 31, 2018		5,408,814			$	4.07

	Number of Option Shares			Weighted Average Grant-Date Fair Value
Non-vested at December 31, 2017		1,261,837		$	3.73
Granted		1,222,000		$	4.57
Vested		(1,283,004	)	$	3.78
Non-vested at December 31, 2018		1,200,833		$	4.04

Weighted-Average Assumptions for Stock Option

	Year Ended December 31,
	2018			2017			2016
Stock Options
Risk-free interest rate		2.52	%		2.06	%		1.60	%
Expected volatility of common stock		61.56	%		72.55	%		78.30	%
Dividend yield		0.00	%		0.00	%		0.00	%
Expected option term (in years)		4.56			5.67			5.57

Weighted-Average Assumptions for ESPP

	Year Ended December 31,
	2018			2017			2016
Employee Stock Purchase Plan
Risk-free interest rate		2.07	%		1.09	%		0.44	%
Expected volatility of common stock		70.41	%		38.34	%		51.65	%
Dividend yield		0.00	%		0.00	%		0.00	%
Expected option term (in years)		0.5			0.5			0.5

Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2018

Equity [Abstract]

Summary of Activity Under the ATM Agreements

The following table summarizes the activity under the ATM agreements for the following periods (in thousands except share price and shares sold):

	Year Ended December 31,
	2018		2017		2016
Gross proceeds		1,562		10,303.0		264
Net proceeds		1,515		9,891.3		159.5
Shares sold		200,000		1,689,436		36,248
Price range	$7.81		$5.30 - 6.98		$6.90 - 7.54

Common Stock Reserved for Future Issuance

The following table summarizes common stock reserved for future issuance at December 31, 2018:

Common Stock reserved for issuance under the ESPP			191,878
Common stock reserved for issuance upon exercise of options outstanding (under the 2004 Plan and 2013 Plan)			6,609,647
Common stock reserved for future equity awards (under the 2013 Plan)			1,494,592
			8,296,117

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Reconciliation of Loss before Income Taxes for Domestic and Foreign Locations

A reconciliation of loss before income taxes for domestic and foreign locations for the years ended December 31, 2018, 2017 and 2016 is as follows:


	2018			2017			2016
United States	$	(14,689,617	)	$	(12,940,362	)	$	(10,892,276	)
Foreign		19,807			33,176			30,050
Loss before income taxes	$	(14,669,810	)	$	(12,907,186	)	$	(10,862,226	)

Reconciliation of Income Tax Benefit (Expense)

A reconciliation of income tax benefit (expense) for the years ended December 31, 2018, 2017 and 2016 is as follows:


Current:	2018			2017			2016
Federal	$	—		$	—		$	1,489
State		—			—			412
Foreign		(5,276	)		(10,158	)		(5,655	)
Total current income tax benefit (expense)		(5,276	)		(10,158	)		(3,754	)
Deferred:
Federal		—			1,329,888			—
State		—			424,320			—
Foreign		—			—			—
Total deferred income tax benefit (expense)		—			1,754,208			—
Total income tax benefit (expense)	$	(5,276	)	$	1,744,050		$	(3,754	)

Components of Deferred Income Taxes

The significant components of deferred income taxes at December 31, 2018 and 2017 are as follows (in thousands):


Deferred tax assets:	2018			2017
Net operating loss carryforwards	$	62,025		$	59,480
Capitalized licenses		286			429
Research tax credits		8,434			8,160
Stock options		3,922			2,585
Other, net		580			572
Total deferred tax assets		75,247			71,226
Deferred tax liabilities
In process R&D		(1,343	)		(1,343	)
Total deferred tax liabilities		(1,343	)		(1,343	)
Net deferred tax assets		73,904			69,883
Valuation allowance		(74,106	)		(70,085	)
Net deferred tax liability	$	(202	)	$	(202	)

Reconciliation of Federal Statutory Income Tax Rate to Effective Income Tax Rate

A reconciliation of the federal statutory income tax rate to the Company’s effective income tax rate is as follows:


	2018			2017			2016
Federal statutory income tax rate		21.0	%		35.0	%		35.0	%
State income taxes, net of federal benefit		6.4			5.2			3.5
Tax credits		1.5			1.1			0.9
Change in valuation allowance		(27.2	)		247.4			(8.4	)
Permanent differences		(0.1	)		(0.3	)		(0.1	)
Expiration of attributes		—			(18.7	)		(17.2	)
Tax Cuts and Jobs Act		—			(253.7	)		—
Stock compensation		(1.7	)		(2.9	)		(13.6	)
Other		0.1			0.4			(0.1	)
Provision for income taxes		0.0	%		13.5	%		0.0	%

Quarterly Financial Data (Tables)

12 Months Ended

Dec. 31, 2018

Quarterly Financial Information Disclosure [Abstract]

Selected Quarterly Financial Information

	Year Ended December 31, 2018
	1st Quarter			2nd Quarter			3rd Quarter			4th Quarter
Selected quarterly financial data:
Total operating expenses	$	4,667		$	3,400		$	7,028		$	492
Net loss		(4,543	)		(3,144	)		(6,780	)		(208	)
Net loss applicable to common stockholders		(4,543	)		(3,144	)		(6,780	)		(208	)
Basic and diluted net loss per common share (1)		(0.12	)		(0.08	)		(0.16	)		(0.00	)

	Year Ended December 31, 2017
	1st Quarter			2nd Quarter			3rd Quarter			4th Quarter
Selected quarterly financial data:
Total operating expenses	$	3,024		$	2,805		$	3,792		$	3,406
Net loss		(3,017	)		(2,789	)		(3,755	)		(1,602	)
Net loss applicable to common stockholders		(3,017	)		(2,789	)		(3,755	)		(1,602	)
Basic and diluted net loss per common share (1)		(0.09	)		(0.08	)		(0.11	)		(0.02	)

(1)	Net loss per share is computed independently for each of the quarters presented. Therefore, the sum of the quarterly net income and loss per share will not necessarily equal the annual per share calculation.

Organization and Summary of Significant Accounting Policies - Additional Information (Detail)		12 Months Ended
	Jan. 01, 2019 Building Copier	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Cash and cash equivalents		$ 62,313,418	$ 27,991,743	$ 24,118,037	$ 22,076,749
Working capital		60,600,000
Cash insured amount		250,000
Goodwill impairment		0	0	0
Impairment of long-lived assets		0	0	0
Research and development		5,300,000	3,900,000	3,100,000
Patent-related expenses		$ 300,000	$ 300,000	$ 400,000
ASU 2016-02 \| Subsequent Event
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Number of properties identified in lease \| Building	2
Number of equipment identified in lease \| Copier	2
Minimum
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Stock option, vesting period		3 years
Maximum
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Stock option, vesting period		4 years

Property and Equipment Net (Detail) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Property Plant And Equipment [Abstract]
Leasehold improvements	$ 16,121	$ 15,742
Furniture and equipment	235,095	233,441
Software	285,446	285,418
Property and Equipment, Gross, Total	536,662	534,601
Less accumulated depreciation and amortization	(483,528)	(471,715)
Property and equipment, net	$ 53,134	$ 62,886

Commitments and Contingencies - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Loss Contingencies [Line Items]
Operating lease, initial term	4 years 1 month
Operating lease expiration period	2021-12
Rent expense	$ 229,613	$ 254,593	$ 256,314
Deferred rent	24,762	253
Research and development expense	5,300,000	3,900,000	3,100,000
Licensing Agreements
Loss Contingencies [Line Items]
Research and development expense	0	$ 0	$ 0
Product Development
Loss Contingencies [Line Items]
Future potential milestone payments	10,000,000
Development Milestone
Loss Contingencies [Line Items]
Future potential milestone payments	33,500,000
Commercialization Milestone
Loss Contingencies [Line Items]
Future potential milestone payments	$ 33,500,000

Estimated Future Annual Minimum Lease Payments under Non-Cancelable Building and Copier Leases (Detail)	Dec. 31, 2018 USD ($)
Commitments And Contingencies Disclosure [Abstract]
2019	$ 182,847
2020	144,234
2021	149,951
2022	1,532
2023	1,404
Total minimum payments	$ 479,968

Share-Based Compensation - Additional Information (Detail) - USD ($)	1 Months Ended	12 Months Ended
	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jun. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for future issuance		8,296,117
Number of outstanding shares		6,609,647	5,514,038	4,432,017	4,133,969
Number of unvested shares		1,200,833	1,261,837
Cash received from stock options exercised		$ 407,196	$ 426,013	$ 829,526
Aggregate intrinsic value		$ 788,423	198,164	$ 414,572
Weighted average contractual life, options outstanding		6 years 3 months 25 days
Weighted average contractual life, options exercisable		6 years 3 months 25 days
Total intrinsic value of options outstanding		$ 23,600,000	13,600,000
Total intrinsic value of options exercisable		$ 22,200,000	$ 12,900,000
Shares reserved, description		shares reserved automatically increase each year by a number equal to the lesser of: (i) 15,000 shares; (ii) 1% of the outstanding shares of common stock on the last day of the immediately preceding fiscal year; or (iii) such lesser amount as determined by the Board
Employee stock purchase plan offering period		6 months
Shares issued under ESPP		7,094
Weighted-average fair value, per option		$ 4.57	$ 3.78	$ 2.64
Share-based compensation expense		$ 6,330,305	$ 4,474,945	$ 3,972,533
Unamortized compensation cost		$ 300,000
Unamortized compensation cost, vesting period		10 days
General and administrative expenses
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense		$ 4,500,000	3,100,000	2,900,000
Research, development and patents expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense		$ 1,800,000	$ 1,400,000	$ 1,100,000
2007 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for future issuance		191,878	300,000
Percentage of employee compensation for purchase of common stock under ESPP		15.00%
Common stock fair market value, percentage		85.00%
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option, vesting period		3 years
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option, vesting period		4 years
Maximum \| 2007 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increase in shares reserved for issuance		15,000
Increase in shares reserved for issuance as percentage of outstanding shares		1.00%
Performance Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of outstanding shares		1,162,000
Number of unvested shares		1,162,000
Stock option, vesting year		2019
2013 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for future issuance		1,494,592				2,500,000
Shares available for future grant		1,494,592
Increase in number of shares of common stock reserved for issuance	1,500,000
2013 Plan \| Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted expiration term		10 years
2013 Plan \| Stock Option \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option, vesting period		3 years
2013 Plan \| Stock Option \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option, vesting period		4 years
2004 Plan \| Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted expiration term		10 years
2004 Plan \| Stock Option \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option, vesting period		3 years
2004 Plan \| Stock Option \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option, vesting period		4 years

Summary of Stock Option Activity and Related Information (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Number of Option Shares
Stock Options, Beginning Balance	5,514,038	4,432,017	4,133,969
Stock Options, Granted	1,222,000	1,195,000	1,158,000
Stock Options, Exercised	(125,391)	(105,579)	(172,585)
Stock Options, Cancelled	(1,000)	(7,400)	(687,367)
Stock Options, Ending Balance	6,609,647	5,514,038	4,432,017
Stock Options, Exercisable at December 31, 2018	5,408,814
Weighted Average Exercise Price, Beginning Balance	$ 4.03	$ 3.47	$ 4.69
Weighted Average Exercise Price, Granted	7.11	6.10	4.00
Weighted Average Exercise Price, Exercised	3.25	4.04	4.81
Weighted Average Exercise Price, Cancelled	4.52	7.76	11.27
Weighted Average Exercise Price, Ending Balance	4.61	$ 4.03	$ 3.47
Weighted Average Exercise Price, Exercisable at December 31, 2018	$ 4.07

Stockholders' Equity - Additional Information (Detail) - USD ($)				12 Months Ended
	Feb. 21, 2018	Feb. 12, 2018	May 22, 2015	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	May 10, 2017
Warrants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise of warrants				750,000	119,047	2,131,700
Proceeds from warrant exercises				$ 2,400,000	$ 400,000	$ 7,600,000
Warrants expiring unexercised							198,020
Warrants, Outstanding				0
At-the-market issuance sales agreement \| MLV
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Sales commission as a percentage of gross proceeds			4.00%
Issuance of common stock, net of offering costs (in shares)				200,000	1,689,436	36,248
Net proceeds from issuance of common stock				$ 1,515,000	$ 9,891,300	$ 159,500
At-the-market issuance sales agreement \| Maximum \| MLV
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock purchase agreement, aggregate amount of common stock agreed to be purchased			$ 30,000,000
Underwritten public offering
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Issuance of common stock, net of offering costs (in shares)		4,419,890
Shares purchase & equity issuance, price per share amount		$ 9.05
Gross proceeds from issuance of common stock	$ 1,100,000	$ 40,000,000
Net proceeds from issuance of common stock		$ 37,400,000
Additional share issuance option term		30 days
Additional shares which underwriters can purchase on option	126,038	662,983

Reconciliation of Income Tax Benefit (Expense) (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Federal			$ 1,489
State			412
Foreign	$ (5,276)	$ (10,158)	(5,655)
Total current income tax benefit (expense)	(5,276)	(10,158)	(3,754)
Federal		1,329,888
State		424,320
Total deferred income tax benefit (expense)		1,754,208
Total income tax benefit (expense)	$ (5,276)	$ 1,744,050	$ (3,754)

Components of Deferred Income Taxes (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Net operating loss carryforwards	$ 62,025	$ 59,480
Capitalized licenses	286	429
Research tax credits	8,434	8,160
Stock options	3,922	2,585
Other, net	580	572
Total deferred tax assets	75,247	71,226
Deferred tax liabilities
In process R&D	(1,343)	(1,343)
Total deferred tax liabilities	(1,343)	(1,343)
Net deferred tax assets	73,904	69,883
Valuation allowance	(74,106)	(70,085)
Net deferred tax liability	$ (202)	$ (202)

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax [Line Items]
Increase of ownership of certain stockholders or public groups in the stock, percentage	50.00%
Increase of ownership of certain stockholders or public groups in the stock, period	3 years
Federal statutory income tax rate	21.00%	35.00%	35.00%
Change in deferred tax asset due to tax cuts and jobs act of 2017		$ 32,700,000
Change in deferred tax asset valuation allowance due to tax cuts and jobs act of 2017		$ 33,400,000
Minimum
Income Tax [Line Items]
Tax cuts and jobs act of 2017, elemination of deductions for executive compensation	$ 1,000,000
Federal
Income Tax [Line Items]
Net operating loss carryforwards	$ 248,900,000
Net operating loss carryforwards, expiration year	2020
Research tax credit carryforwards	$ 6,960,000
Research and Development Credits, expiration period	2024
California
Income Tax [Line Items]
Net operating loss carryforwards	$ 139,600,000
Net operating loss carryforwards, expiration year	2028
Research tax credit carryforwards	$ 1,900,000

Reconciliation of Federal Statutory Income Tax Rate to Effective Income Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Federal statutory income tax rate	21.00%	35.00%	35.00%
State income taxes, net of federal benefit	6.40%	5.20%	3.50%
Tax credits	1.50%	1.10%	0.90%
Change in valuation allowance	(27.20%)	247.40%	(8.40%)
Permanent differences	(0.10%)	(0.30%)	(0.10%)
Expiration of attributes		(18.70%)	(17.20%)
Tax Cuts and Jobs Act		(253.70%)
Stock compensation	(1.70%)	(2.90%)	(13.60%)
Other	0.10%	0.40%	(0.10%)
Provision for income taxes	0.00%	13.50%	0.00%

Revenue Recognition - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2011
Revenue Recognition Milestone Method [Line Items]
Deferred revenue related to research and development services	$ 1,694,163	$ 1,694,163
Kissei Pharmaceutical Co., Ltd
Revenue Recognition Milestone Method [Line Items]
Deferred revenue related to research and development services				$ 2,500,000
Revenue relating to research and development services	$ 0	$ 0	$ 0

Fair Value Measurements - Additional Information (Detail) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Level 1 \| Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents, fair value	$ 677,594	$ 666,265

Balance Sheet Details - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property Plant And Equipment Disclosure [Line Items]
Depreciation and amortization	$ 25,881	$ 28,098	$ 14,127
Minimum
Property Plant And Equipment Disclosure [Line Items]
Property and Equipment, useful lives	3 years
Maximum
Property Plant And Equipment Disclosure [Line Items]
Property and Equipment, useful lives	5 years

Joint Venture - Additional Information (Detail) - USD ($)	1 Months Ended	12 Months Ended
	Apr. 30, 2018	Dec. 31, 2018
Schedule Of Equity Method Investments [Line Items]
Proceed from dissolution of joint venture and liquidation of investments		$ 636,524
Zhejiang Sunmy Bio Medical Co Ltd
Schedule Of Equity Method Investments [Line Items]
Investment in joint venture, percentage		50.00%
Zhejiang Sunmy Bio Medical Co Ltd \| Beijing Medfron Medical Technologies Co Ltd
Schedule Of Equity Method Investments [Line Items]
Investment in joint venture, percentage		50.00%
Proceed from dissolution of joint venture and liquidation of investments	$ 600,000

Employee Savings Plan - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Postemployment Benefits [Abstract]
Discretionary contributions to employee savings plan	$ 76,903	$ 65,995	$ 66,289

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2018	Dec. 31, 2017
Statement Of Financial Position [Abstract]
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	42,081,306	36,452,893
Common stock, shares outstanding	42,081,306	36,452,893

Accrued Liabilities (Detail) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Payables And Accruals [Abstract]
Accrued compensation	$ 1,137,869	$ 952,470
Research and development costs	226,597	122,665
Professional services fees	18,763	144,105
Other	191,932	141,504
Total accrued liabilities	$ 1,575,161	$ 1,360,744