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Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2019	May 06, 2019
Document And Entity Information [Abstract]
Entity Registrant Name	Clearside Biomedical, Inc.
Amendment Flag	false
Document Period End Date	Mar. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Trading Symbol	CLSD
Document Type	10-Q
Entity Central Index Key	0001539029
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Common Stock, Shares Outstanding		37,595,551

Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 32,950	$ 8,043
Short-term investments	1,988	32,835
Prepaid expenses	497	2,049
Other current assets	33	17
Total current assets	35,468	42,944
Property and equipment, net	755	790
Operating lease right-of-use asset	925
Restricted cash	360	360
Other assets	26	26
Total assets	37,534	44,120
Current liabilities:
Accounts payable	5,258	6,869
Accrued liabilities	4,520	2,923
Current portion of long-term debt	1,389	556
Current portion of operating lease liabilities	499
Current portion of deferred rent		128
Total current liabilities	11,666	10,476
Long-term debt	8,647	9,419
Operating lease liabilities	1,130
Deferred rent		605
Total liabilities	21,443	20,500
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.001 par value; 10,000,000 shares authorized and no shares issued at March 31, 2019 and December 31, 2018
Common stock, $0.001 par value; 100,000,000 shares authorized at March 31, 2019 and December 31, 2018; 36,782,920 and 32,119,227 shares issued and outstanding at March 31, 2019 and December 31, 2018, respectively	37	32
Additional paid-in capital	238,345	230,475
Accumulated deficit	(222,291)	(206,887)
Total stockholders’ equity	16,091	23,620
Total liabilities and stockholders’ equity	$ 37,534	$ 44,120

Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares, issued	36,782,920	32,119,227
Common stock, shares outstanding	36,782,920	32,119,227

Statements of Operations - USD ($) $ in Thousands	3 Months Ended
Statements of Operations - USD ($) $ in Thousands	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Collaboration revenue	$ 45
Type of Revenue [Extensible List]	clsd:CollaborationMember	clsd:CollaborationMember
Operating expenses:
Research and development	$ 10,967	$ 13,379
General and administrative	4,384	3,074
Total operating expenses	15,351	16,453
Loss from operations	(15,306)	(16,453)
Other expense, net	(98)	(154)
Net loss	$ (15,404)	$ (16,607)
Net loss per share of common stock — basic and diluted	$ (0.45)	$ (0.62)
Weighted average shares outstanding — basic and diluted	34,144,209	26,818,137

Statement of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In-Capital	Accumulated Deficit	Accumulated Other Comprehensive Loss
Beginning balance at Dec. 31, 2017	$ 21,415	$ 25	$ 145,618	$ (124,220)	$ (8)
Beginning balance, shares at Dec. 31, 2017		25,354,651
Cumulative effect of accounting change	159			151	$ 8
Issuance of common shares from follow-on public offering	79,581	$ 7	79,574
Issuance of common stock for follow-on public offering, shares		6,538,462
Exercise of stock options	237		237
Exercise of stock options, shares		53,920
Share-based compensation expense	1,138		1,138
Net loss	(16,607)			(16,607)
Ending balance at Mar. 31, 2018	85,923	$ 32	226,567	(140,676)
Ending balance, shares at Mar. 31, 2018		31,947,033
Beginning balance at Dec. 31, 2018	23,620	$ 32	230,475	(206,887)
Beginning balance, shares at Dec. 31, 2018		32,119,227
Issuance of common shares from at-the-market sales agreement	6,627	$ 5	6,622
Issuance of common shares from at-the-market sales agreement, shares		4,660,966
Exercise of stock options	1		1
Exercise of stock options, shares		2,727
Share-based compensation expense	1,247		1,247
Net loss	(15,404)			(15,404)
Ending balance at Mar. 31, 2019	$ 16,091	$ 37	$ 238,345	$ (222,291)
Ending balance, shares at Mar. 31, 2019		36,782,920

Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
Statements of Cash Flows - USD ($) $ in Thousands	Mar. 31, 2019	Mar. 31, 2018
Operating activities
Net loss	$ (15,404)	$ (16,607)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	53	47
Share-based compensation expense	1,247	1,138
Non-cash interest expense	46	49
Accretion of debt discount	15	49
Amortization and accretion on available-for-sale investments, net	(103)	(43)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	1,536	(613)
Other assets and liabilities	(29)	12
Accounts payable and accrued liabilities	(14)	341
Deferred rent		(26)
Net cash used in operating activities	(12,653)	(15,653)
Investing activities
Maturities of available-for-sale investments	30,950	20,970
Purchase of available-for-sale investments		(8,725)
Acquisition of property and equipment	(18)
Net cash provided by investing activities	30,932	12,245
Financing activities
Proceeds from at-the-market sales agreement, net of issuance costs	6,627
Proceeds from follow-on public offering, net of issuance costs		79,581
Proceeds from exercise of stock options	1	237
Payments made on long-term debt		(800)
Net cash provided by financing activities	6,628	79,018
Net increase in cash, cash equivalents and restricted cash	24,907	75,610
Cash, cash equivalents and restricted cash, beginning of period	8,403	9,584
Cash, cash equivalents and restricted cash, end of period	33,310	85,194
Reconciliation of cash, cash equivalents and restricted cash
Cash and cash equivalents	32,950	84,834
Restricted cash	360	360
Cash, cash equivalents and restricted cash, end of period	$ 33,310	$ 85,194

The Company

3 Months Ended

Mar. 31, 2019

Organization Consolidation And Presentation Of Financial Statements [Abstract]

The Company

1. The Company

Clearside Biomedical, Inc. (the “Company”) is a late-stage clinical biopharmaceutical company developing first-in-class pharmacological therapies to restore and preserve vision for people with serious eye diseases. The Company’s current product candidates focus on treatments for diseases affecting the retina and choroid and are injected into the suprachoroidal space (“SCS”) using its proprietary SCS Microinjector™. Incorporated in the State of Delaware on May 26, 2011, the Company has its corporate headquarters in Alpharetta, Georgia.

The Company’s activities since inception have primarily consisted of developing product and technology rights, raising capital and performing research and development activities. The Company has no current source of revenue to sustain present activities, and does not expect to generate meaningful revenue until and unless the Company receives regulatory approval of and successfully commercializes, its product candidates. The Company is subject to a number of risks and uncertainties similar to those of other life science companies at a similar stage of development, including, among others, the need to obtain adequate additional financing, successful development efforts, regulatory approval of products, compliance with government regulations, successful commercialization of potential products, protection of proprietary technology and dependence on key individuals.

Liquidity

The Company has funded its operations primarily through the sale of convertible preferred stock and common stock and the issuance of long-term debt. On June 30, 2017, the Company entered into an at-the-market sales agreement (“the ATM agreement”) with Cowen and Company LLC (“Cowen”) under which the Company may offer and sell, from time to time at its sole discretion, shares of its common stock having an aggregate offering price of up to $50.0 million through Cowen acting as sales agent. As of March 31, 2019, the Company had sold 4.7 million shares of its common stock for net proceeds of $6.6 million under the ATM agreement. The Company’s registration statement on Form S-3 contemplated under the ATM agreement was declared effective by the SEC on July 13, 2017. The registration statement on Form S-3 includes a prospectus supplement covering the offering up to $18.5 million of shares of common stock over the 12 months ending March 15, 2020 in accordance with the ATM agreement.

The Company will need to obtain additional financing to fund future operations, including completing the development and commercialization of its primary product candidates. The Company will need to obtain additional financing to conduct additional trials for the regulatory approval of its product candidates if requested by regulatory bodies, and to complete the development of any additional product candidates. If such products were to receive regulatory approval, the Company may need to prepare for the potential commercialization of its product candidates and fund the commercial launch of the products, if the Company decides to commercialize the products on its own. Moreover, the Company’s fixed expenses such as rent and other contractual commitments are substantial and are expected to increase in the future.

The Company had cash, cash equivalents and short-term investments of $34.9 million as of March 31, 2019. The Company has suffered recurring losses and negative cash flows from operations since inception and anticipates incurring additional losses until such time, if ever, that it can obtain approval from the U.S. Food and Drug Administration (the “FDA”) to market, and then generate significant sales of its lead product candidate, XIPERE™. In the absence of product or other revenues, the amount, timing, nature or source of which cannot be predicted, the Company’s losses will continue as it conducts its research and development activities and prepares for the anticipated commercial launch of XIPERE. The Company will need additional financing to fund its operations and to commercialize XIPERE and may finance future cash needs through public or private equity offerings, license agreements, debt financings, collaborations, strategic alliances and marketing or distribution arrangements.

Based on its current research and development plans, including the discontinuation of clinical development of XIPERE together with an anti-vascular endothelial growth factor agent for the treatment of retinal vein occlusion, its plans to reduce certain administrative expenses and its timing expectations related to the approval of its New Drug Application (“NDA”) submission, the Company expects that its existing cash, cash equivalents and short-term investments will enable it to fund its operating expenses and capital expenditure requirements into the first quarter of 2020. Accordingly, the Company has plans to mitigate its going concern risk by raising additional capital, potentially in a combination of equity or debt financings, or by entering into potential collaborations, partnering and other strategic arrangements. The Company has based this estimate on assumptions that may prove to be wrong, and the Company could exhaust its capital resources sooner than it expects. These conditions raise substantial doubt about the Company’s ability to continue as a going concern within one year after the date these financial statements are being issued.

The Company’s financial statements have been prepared on a going concern basis, which contemplates the realization of assets and satisfaction of liabilities in the normal course of business. The financial statements do not include any adjustments to reflect the possible future effects on the recoverability and classification of recorded asset amounts or the amounts and classification of liabilities that might result should the Company be unable to continue as a going concern.

Significant Accounting Policies

3 Months Ended

Mar. 31, 2019

Accounting Policies [Abstract]

Significant Accounting Policies

2. Significant Accounting Policies

Basis of Presentation

The Company’s financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”).

Unaudited Interim Financial Information

The accompanying balance sheet as of March 31, 2019, statements of operations for the three months ended March 31, 2019 and 2018, statements of stockholders’ equity for the three months ended March 31, 2019 and 2018 and statements of cash flows for the three months ended March 31, 2019 and 2018 are unaudited. The unaudited interim financial statements have been prepared on the same basis as the annual financial statements and, in the opinion of management, reflect all adjustments, which include normal recurring adjustments, necessary for the fair presentation of the Company’s financial position as of March 31, 2019, its results of its operations for the three months ended March 31, 2019 and 2018, its changes in stockholders’ equity for the three months ended March 31, 2019 and 2018 and its cash flows for the three months ended March 31, 2019 and 2018. The financial data and other information disclosed in these notes related to the three months ended March 31, 2019 and 2018 are unaudited. The results for the three months ended March 31, 2019 are not indicative of results to be expected for the year ending December 31, 2019, any other interim periods or any future year or period. These unaudited financial statements should be read in conjunction with the audited financial statements and related footnotes, which are included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2018.

Use of Estimates

The preparation of financial statements in conformity with U.S. 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 reported amounts of income and expenses during the reporting periods. Significant items subject to such estimates and assumptions include the accounting for useful lives to calculate depreciation and amortization, clinical expense accruals, share-based compensation expense and income tax valuation allowance. Actual results could differ from these estimates.

Research and Development Costs

Research and development costs are charged to expense as incurred and include:

•

employee-related expenses, including salaries, benefits, travel and share-based compensation expense for research and development personnel;

•

expenses incurred under agreements with contract research organizations, contract manufacturing organizations and consultants that conduct clinical trials and preclinical studies;

•

costs associated with nonclinical and clinical development activities;

•

costs associated with submitting regulatory approval applications for the Company’s product candidates;

•

costs associated with training physicians on the suprachoroidal injection procedure and educating and providing them with appropriate product candidate information;

•

costs associated with technology and intellectual property licenses;

•

costs for the Company’s research and development facility; and

•

depreciation expense for assets used in research and development activities.

Costs for certain development activities, such as clinical trials, are recognized based on an evaluation of the progress to completion of specific tasks using data such as patient enrollment, clinical site activations, or information provided to the Company by its vendors on their actual costs incurred. Payments for these activities are based on the terms of the individual arrangements, which may differ from the patterns of costs incurred, and are reflected in the financial statements as prepaid or accrued expense. No material adjustments to these estimates have been recorded in these financial statements.

Share-Based Compensation

Compensation cost related to share-based awards granted to employees is measured based on the estimated fair value of the award at the grant date. The Company estimates the fair value of stock options using a Black-Scholes option pricing model. Compensation expense for options granted to non-employees is determined as the fair value of consideration received or the fair value of the equity instruments issued, whichever is more reliably measured. The fair value of awards granted to non-employees is re-measured each period until the related service is complete. Share-based compensation costs are expensed on a straight-line basis over the relevant vesting period.

Compensation cost related to shares purchased through the Company’s employee stock purchase plan, which is considered compensatory, is based on the estimated fair value of the shares on the offering date, including consideration of the discount and the look back period. The Company estimates the fair value of the shares using a Black-Scholes option pricing model. Compensation expense is recognized over the six-month withholding period prior to the purchase date.

All share-based compensation costs are recorded in general and administrative or research and development costs in the statements of operations based upon the underlying employees’ roles within the Company.

Cash Equivalents

Cash equivalents consist of short-term, highly liquid investments with an original term of three months or less at the date of purchase.

Short-Term Investments

Short-term investments are investments with original maturities of between 90 and 365 days when purchased and are comprised of commercial paper and treasury bills. The Company classifies its short-term investments as available-for-sale securities. Short-term investments are recorded at fair value and unrealized gains and losses are recorded within interest income. In addition, the Company evaluates the short-investments with unrealized losses to determine whether such losses are other-than-temporary.

Concentration of Credit Risk Arising From Cash Deposits in Excess of Insured Limits

The Company maintains its cash in bank deposits that at times may exceed federally insured limits. The Company has not experienced any loss in such accounts. The Company believes it is not exposed to any significant risks with respect to its cash balances.

Recent Accounting Pronouncements

In February 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-02, Leases (ASC 842), and subsequently issued updates as part of ASU 2018-11, Leases, Targeted Improvements. The new guidance requires organizations that lease assets with lease terms of more than 12 months to recognize assets and liabilities for the rights and obligations created by those leases on their balance sheets. The Company adopted the ASC 842 effective January 1, 2019 using the optional transition method, did not restate any prior periods and adopted the package of practical expedients. Under the package of practical expedients permitted by the new standard, the Company does not have to reassess whether contracts are or contain leases, the classification of leases or whether initial direct costs should be capitalized. The adoption of the new standard resulted in the recognition of a right-of use asset of $1.0 million and lease obligations of $1.7 million on the Company’s balance sheet as of January 1, 2019. The adoption did not have a material impact on the Company’s statements of operations or cash flows.

In June 2018, the FASB issued ASU 2018-07, Compensation-Stock Compensation: Improvements to Nonemployee Shared-Based Payment Accounting. The ASU update expands the scope of Topic 718 to include share-based payment transactions for acquiring goods and services from nonemployees. The Company adopted ASU 2018-07 effective January 1, 2019, and the adoption did not have a material impact on its financial statements and related disclosures.

Property and Equipment, Net

3 Months Ended

Mar. 31, 2019

Property Plant And Equipment [Abstract]

Property and Equipment, Net

3. Property and Equipment, Net

Property and equipment, net consisted of the following (dollar amounts in thousands):

	Estimated Useful Lives (Years)	March 31, 2019			December 31, 2018
Furniture and fixtures	5	$	400		$	382
Machinery and equipment	5		121			121
Computer equipment	3		19			19
Leasehold improvements	Lesser of useful life or remaining lease term		677			677
			1,217			1,199
Less: Accumulated depreciation			(462	)		(409	)
		$	755		$	790

Accrued Liabilities

3 Months Ended

Mar. 31, 2019

Payables And Accruals [Abstract]

Accrued Liabilities

4. Accrued Liabilities

Accrued liabilities consisted of the following (in thousands):

	March 31,		December 31,
	2019		2018
Accrued research and development	$	3,268	$	1,263
Accrued marketing		366		47
Accrued bonuses		405		1,088
Accrued professional fees		129		63
Accrued vacation		169		103
Accrued interest payable		—		76
Accrued expense		183		283
	$	4,520	$	2,923

Long-Term Debt

3 Months Ended

Mar. 31, 2019

Debt Disclosure [Abstract]

Long-Term Debt

5. Long-Term Debt

Loan and Security Agreements

In September 2016, the Company entered into an amended and restated loan and security agreement, which was subsequently amended on October 31, 2017 (as amended, the “1^st A&R loan agreement”) with Silicon Valley Bank (“SVB”), MidCap Funding XII Trust and MidCap Financial Trust, which amended and restated in its entirety the Company’s prior loan and security agreement. The 1^st A&R loan agreement provided for new term loans of up to $15.0 million, with a floating interest rate equal to 7% plus the greater of (i) the 30-day U.S. LIBOR, as reported in the Wall Street Journal on the last business day of the month that immediately precedes the month in which the interest will accrue, or (ii) 0.50%.

Under the terms of the 1^st A&R loan agreement, an initial tranche of $8.0 million was advanced on September 28, 2016. The draw period for the remaining $7.0 million available under the 1^st A&R loan agreement expired on March 31, 2018. The Company was required to pay accrued interest only on the outstanding $8.0 million balance through December 31, 2017, followed by 30 equal payments of principal and accrued interest. The Company had the option to prepay the outstanding balance of the term loans in full, subject to a prepayment fee of 2% of the original principal amount of the aggregate term loans for any prepayments through May 31, 2020. A final payment of $0.5 million was due at maturity of the loan on June 1, 2020, or upon the prepayment of the facility or the acceleration of amounts due under the facility as a result of an event of default, and was being accreted in long-term debt over the life of the loan. Of the $8.0 million borrowed, $5.3 million was used to repay all amounts outstanding under the original loan agreement. Closing costs incurred in the refinancing portion of the loan were recorded as expense while the financing costs for the new portion of the loan are recorded in long-term debt and being accreted over the life of the loan. Upon repayment of the original loan agreement, all remaining closing costs associated with the original loan agreement were being accreted to long-term debt over the life of the 1^st A&R loan agreement.

On May 14, 2018, the Company entered into a second amended and restated loan and security agreement (the “2^nd A&R Loan Agreement”) with SVB, MidCap Funding III Trust and MidCap Financial Trust (together, “MidCap” and collectively with SVB, the “Lenders”), which amended and restated in its entirety the 1^st A&R loan agreement. The 2^nd A&R Loan Agreement provides for new term loans of up to $20.0 million, with a floating interest rate equal to 6.50% plus the greater of (i) the 30-day U.S. LIBOR, as reported in the Wall Street Journal on the last business day of the month that immediately precedes the month in which the interest will accrue, or (ii) 1.89%.

The Company borrowed an initial tranche of $10.0 million on May 14, 2018, of which $7.0 million was used to repay all amounts outstanding under the 1^st A&R loan agreement, including fees associated with the final payment. The prepayment fees were waived. Of the remaining $10.0 million under the 2^nd A&R Loan Agreement, $5.0 million became available for draw but was not drawn by the Company, and the other $5.0 million is not available for draw.

The Company is required to pay accrued interest only on the $10 million borrowed under the 2^nd A&R Loan Agreement through October 31, 2019, followed by consecutive equal monthly payments of principal and interest in arrears continuing through the maturity date of October 1, 2022. The Company has the option to prepay the outstanding balance in full, subject to a prepayment fee of 3% of the original principal amount for any prepayment prior to May 14, 2019 or 2% of the original principal amount for any prepayment on or after May 14, 2019 but prior to October 1, 2022. A final payment of 5.50% of the aggregate borrowed amount is due at maturity of the loan on October 1, 2022, or upon the prepayment of the facility or the acceleration of amounts due under the facility as a result of an event of default.

The borrowings under the 2^nd A&R Loan Agreement are secured by substantially all of the Company’s assets, except that the collateral does not include any of the Company’s intellectual property. However, pursuant to the terms of a negative pledge arrangement, the Company has agreed not to encumber any of its intellectual property.

Interest expense on the borrowings under the loan agreements described above was $225,000 and $161,000 for the three months ended March 31, 2019 and 2018, respectively. Accretion of the scheduled final payment was $46,000 and $49,000 for the three months ended March 31, 2019 and 2018, respectively. Accretion of the deferred debt issuance costs was $15,000 and $49,000 for the three months ended March 31, 2019 and 2018, respectively.

As of March 31, 2019, the scheduled payments for the 2^nd A&R Loan Agreement, including the scheduled final payment in 2022, were as follows (in thousands):

Year Ending December 31,	Principal		Interest and Final Payment		Total
2019	$	556	$	635	$	1,191
2020		3,333		651		3,984
2021		3,333		366		3,699
2022		2,778		638		3,416
	$	10,000	$	2,290	$	12,290

Common Stock

3 Months Ended

Mar. 31, 2019

Equity [Abstract]

Common Stock

6. Common Stock

The Company’s amended and restated certificate of incorporation authorizes the Company to issue 100,000,000 shares of $0.001 par value common stock. As of March 31, 2019 and December 31, 2018, there were 36,782,920 and 32,119,227 shares of common stock outstanding, respectively.

Stock Purchase Warrants

3 Months Ended

Mar. 31, 2019

Stock Purchase Warrants [Abstract]

Stock Purchase Warrants

7. Stock Purchase Warrants

In September 2016, in connection with the 1^st A&R loan agreement (see Note 5), the Company issued warrants to purchase up to 29,796 shares of common stock at a price per share of $10.74. The warrants expire in September 2026, or earlier upon the occurrence of specified mergers or acquisitions of the Company, and are immediately exercisable. The warrants were recorded in equity and had a weighted average remaining life of 7.5 years as of March 31, 2019.

Share-Based Compensation

3 Months Ended

Mar. 31, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Share-Based Compensation

8. Share-Based Compensation

Share-based compensation is accounted for in accordance with the provisions of ASC 718, Compensation-Stock Compensation.

Stock Options

The Company has granted stock option awards to employees, directors and consultants from its 2011 Stock Incentive Plan (the “2011 Plan”) and its 2016 Equity Incentive Plan (the “2016 Plan”). The estimated fair value of options granted is determined as of the date of grant using the Black-Scholes option pricing model. The resulting fair value is recognized ratably over the requisite service period, which is generally the vesting period of the awards.

Share-based compensation expense for options granted under the 2011 Plan and the 2016 Plan is reflected in the statements of operations as follows (in thousands):

	Three Months Ended March 31,
	2019		2018
Research and development	$	462	$	431
General and administrative		775		702
Total	$	1,237	$	1,133

The following table summarizes the activity related to stock options during the three months ended March 31, 2019:

				Weighted
	Number of			Average
	Shares			Exercise Price
Options outstanding at January 1, 2019		3,463,096		$	6.62
Granted		1,532,600			1.24
Exercised		(2,727	)		0.40
Forfeited		(160,080	)		6.25
Options outstanding at March 31, 2019		4,832,889			6.62

Options exercisable at December 31, 2018		1,583,749			5.63

Options exercisable at March 31, 2019		1,593,506			5.77

As of March 31, 2019, the Company had $10.3 million of unrecognized compensation expense related to unvested stock options, which is expected to be recognized over a weighted average period of 2.7 years.

Employee Stock Purchase Plan

In January 2016, the Company’s board of directors adopted and approved, and in January 2016 the Company’s stockholders approved, the Clearside Biomedical, Inc. 2016 Employee Stock Purchase Plan (the “2016 ESPP”) which became effective on June 1, 2016. The first offering period for the 2016 ESPP commenced January 1, 2017. The 2016 ESPP is considered a compensatory plan and the fair value of the discount and the look-back period are estimated using the Black-Scholes option pricing model and expense is recognized over the six month withholding period prior to the purchase date. The Company has issued a total of 22,287 shares of common stock purchased under the 2016 ESPP. The Company has recorded $9,800 and $5,000 of share-based compensation expense for the three months ended March 31, 2019 and 2018, respectively, in the statements of operations for the estimated number of shares to be purchased on the next purchase date following the conclusion of the applicable reporting period.

Commitment and Contingencies

3 Months Ended

Mar. 31, 2019

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

9. Commitments and Contingencies

Lease Commitment Summary

In November 2016, the Company signed an office lease agreement to lease approximately 20,000 square feet of office space in Alpharetta, Georgia for its corporate headquarters. The lease agreement is for a 6.5 year term with a renewal option for one additional five-year term. Rental payments are $35,145 per month subject to an increase of 3% per year. Rent expense under this lease is recognized on a straight-line basis over the term of the lease. In addition, the lease agreement requires payment of the pro-rata share of the annual operating expenses associated with the premises. The Company relocated to this space in March 2017.

In August 2018, the Company signed an office lease agreement to lease approximately 3,500 square feet of office space in Berkeley, California for its commercial operations. The lease agreement is for a two-year term with a renewal option for an additional one-year term. Rental payments are $12,775 per month subject to a 3% increase per year. Rent expense under this lease is recognized on a straight-line basis over the term of the lease. The Company will pay a pro-rata share of the annual operating expenses associated with the premises.

The Company’s operating leases included on the balance sheet are as follows (in thousands):

	March 31, 2019
Operating lease right-of-use asset	$	925

Liabilities
Current portion of operating lease liabilities	$	499
Operating lease liabilities		1,130
Total operating lease liabilities	$	1,629

The Company recognizes a right-of-use asset for the right to use the underlying asset for the lease term, and a lease liability, which represents the present value of the Company’s obligation to make payments over the lease term. The renewal option is not included in the calculation of the right-of-use asset and the lease liabilities as the Company has not yet determined if the leases will be renewed. The present value of the lease payments is calculated using an incremental borrowing rate as the Company’s leases do not provide an implicit interest rate. At March 31, 2019, the Company’s weighted average discount rate was 5.3% and the weighted average lease term was 2.9 years.

Total future undiscounted minimum lease payments were as follows at March 31, 2019 (in thousands):

Year Ending December 31,
2019	$	471
2020		574
2021		496
2022		511
2023		393
Total minimum lease payments	$	2,445

Equipment leases with an initial term of 12 months or less are not recorded with operating lease liabilities. The Company recognizes expense for these on a straight-line basis over the lease term. The equipment leases were deemed to be immaterial.

Rent expense was $100,000 and $58,000 for the three months ended March 31, 2019 and 2018, respectively. Cash payments included in operating activities on the statement of cash flows for operating lease liabilities was $129,000 for the three months ended March 31, 2019.

Contract Service Providers

In the course of the Company’s normal business operations, it has agreements with contract service providers to assist in the performance of its research and development, clinical research and manufacturing. Substantially all of these contracts are on an as needed basis.

Collaboration Agreements

3 Months Ended

Mar. 31, 2019

Collaboration Agreements [Abstract]

Collaboration Agreements

10. Collaboration Agreements

The Company has periodically entered into other short-term collaboration agreements, generally with performance obligations of one to two months, to evaluate the potential use of its proprietary SCS Microinjector with third-party product candidates for the treatment of various diseases. Funds received from these collaboration agreements are recognized as revenue over the term of the agreement. The Company recorded $45,000 of revenue from these collaboration agreements during the three months ended March 31, 2019.

Available-for-Sale Investments

3 Months Ended

Mar. 31, 2019

Investments Debt And Equity Securities [Abstract]

Available-for-Sale Investments

11. Available-for-Sale Investments

The following table summarizes the Company’s available-for-sale investments (in thousands):

	March 31, 2019
	Amortized		Unrealized		Fair
	Cost		Losses		Value
Commercial paper	$	1,988	$	—	$	1,988
Total available-for-sale investments	$	1,988	$	—	$	1,988

Fair Value Measurements

3 Months Ended

Mar. 31, 2019

Fair Value Disclosures [Abstract]

Fair Value Measurements

12. Fair Value Measurements

The Company records certain financial assets and liabilities at fair value in accordance with the provisions of ASC Topic 820, Fair Value Measurements and Disclosures, on fair value measurements. As defined in the guidance, fair value, defined as an exit price, represents the amount that would be received to sell an asset or pay to transfer a liability in an orderly transaction between market participants. As a result, fair value is a market-based approach that should be determined based on assumptions that market participants would use in pricing an asset or a liability. As a basis for considering these assumptions, the guidance defines a three-tier value hierarchy that prioritizes the inputs used in the valuation methodologies in measuring fair value.

•

Level 1—Unadjusted quoted prices in active, accessible markets for identical assets or liabilities.

•

Level 2—Other inputs that are directly or indirectly observable in the marketplace.

•

Level 3—Unobservable inputs that are supported by little or no market activity.

The fair value hierarchy also requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value.

The Company’s material financial instruments at March 31, 2019 and December 31, 2018 consisted primarily of cash and cash equivalents, short-term investments and long-term debt. The fair value of cash and cash equivalents, government bonds, other current assets and accounts payable approximate their respective carrying values due to the short term nature of these instruments and are classified as Level 1 in the fair value hierarchy. The fair value of long-term debt approximates the carrying value due to variable interest rates that correspond to market rates is classified as Level 1 in the fair value hierarchy. The Company has determined its short-term investments, comprised of treasury bills and commercial paper, to be Level 2 in the fair value hierarchy. The fair value was determined using a market approach, based on prices and other relevant information generated by market transactions involving similar assets. The short-term investments consist of investments with original maturity dates from date of acquisition of 90 to 365 days and are classified as available-for-sale.

There were no significant transfers between Levels 1, 2 and 3 during the three months ended March 31, 2019 and the year ended December 31, 2018.

The following tables summarize the fair value of financial assets that are measured at fair value and the classification by level of input within the fair value hierarchy (in thousands):

	March 31, 2019
	Level 1		Level 2		Level 3		Recorded Value
Financial Assets:
Cash and money markets	$	32,950	$	—	$	—	$	32,950
Restricted cash money market		360		—		—		360
Commercial paper		—		1,988		—		1,988
Total financial assets	$	33,310	$	1,988	$	—	$	35,298

	December 31, 2018
	Level 1		Level 2		Level 3		Recorded Value
Financial Assets:
Cash and money markets	$	8,042	$	—	$	—	$	8,042
Restricted cash money market		360		—		—		360
Treasury bills		7,490		—		—		7,490
Commercial paper		—		25,346		—		25,346
Total financial assets	$	15,892	$	25,346	$	—	$	41,238

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Net Loss per Share

3 Months Ended

Mar. 31, 2019

Earnings Per Share [Abstract]

Net Loss Per Share

13. Net Loss Per Share

Basic net loss per share is calculated by dividing the net loss by the weighted average number of shares of common stock outstanding for the period, without consideration of the dilutive effect of potential common stock equivalents. Diluted net loss per share gives effect to all dilutive potential shares of common stock outstanding during this period. For all periods presented, the Company’s potential common stock equivalents, which included stock options and stock purchase warrants, have been excluded from the computation of diluted net loss per share as their inclusion would have the effect of reducing the net loss per share. Therefore, the denominator used to calculate both basic and diluted net loss per share is the same in all periods presented. The Company’s potential common stock equivalents that have been excluded from the computation of diluted net loss per share for all periods presented because of their antidilutive effect consisted of the following:

	Three Months Ended March 31,
	2019		2018
Outstanding stock options		4,832,889		3,135,929
Stock purchase warrants		29,796		29,796
		4,862,685		3,165,725

Significant Accounting Policies (Policies)

3 Months Ended

Mar. 31, 2019

Accounting Policies [Abstract]

Basis of Presentation

The Company’s financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”).

Unaudited Interim Financial Information

Use of Estimates

Research and Development Costs

Research and development costs are charged to expense as incurred and include:

•

employee-related expenses, including salaries, benefits, travel and share-based compensation expense for research and development personnel;

•

expenses incurred under agreements with contract research organizations, contract manufacturing organizations and consultants that conduct clinical trials and preclinical studies;

•

costs associated with nonclinical and clinical development activities;

•

costs associated with submitting regulatory approval applications for the Company’s product candidates;

•

costs associated with training physicians on the suprachoroidal injection procedure and educating and providing them with appropriate product candidate information;

•

costs associated with technology and intellectual property licenses;

•

costs for the Company’s research and development facility; and

•

depreciation expense for assets used in research and development activities.

Share-Based Compensation

Cash Equivalents

Cash equivalents consist of short-term, highly liquid investments with an original term of three months or less at the date of purchase.

Short-Term Investments

Concentration of Credit Risk Arising From Cash Deposits in Excess of Insured Limits

Recent Accounting Pronouncements

Property and Equipment, Net (Tables)

3 Months Ended

Mar. 31, 2019

Property Plant And Equipment [Abstract]

Schedule of Property and Equipment, Net

Property and equipment, net consisted of the following (dollar amounts in thousands):

	Estimated Useful Lives (Years)	March 31, 2019			December 31, 2018
Furniture and fixtures	5	$	400		$	382
Machinery and equipment	5		121			121
Computer equipment	3		19			19
Leasehold improvements	Lesser of useful life or remaining lease term		677			677
			1,217			1,199
Less: Accumulated depreciation			(462	)		(409	)
		$	755		$	790

Accrued Liabilities (Tables)

3 Months Ended

Mar. 31, 2019

Payables And Accruals [Abstract]

Schedule of Accrued Liabilities

Accrued liabilities consisted of the following (in thousands):

	March 31,		December 31,
	2019		2018
Accrued research and development	$	3,268	$	1,263
Accrued marketing		366		47
Accrued bonuses		405		1,088
Accrued professional fees		129		63
Accrued vacation		169		103
Accrued interest payable		—		76
Accrued expense		183		283
	$	4,520	$	2,923

Long-Term Debt (Tables)

3 Months Ended

Mar. 31, 2019

Second Amended and Restated Loan and Security Agreement

Scheduled Payments for the Second Amended and Restated Loan and Security Agreement

As of March 31, 2019, the scheduled payments for the 2^nd A&R Loan Agreement, including the scheduled final payment in 2022, were as follows (in thousands):

Year Ending December 31,	Principal		Interest and Final Payment		Total
2019	$	556	$	635	$	1,191
2020		3,333		651		3,984
2021		3,333		366		3,699
2022		2,778		638		3,416
	$	10,000	$	2,290	$	12,290

Share-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Share-based Compensation Expense

Share-based compensation expense for options granted under the 2011 Plan and the 2016 Plan is reflected in the statements of operations as follows (in thousands):

	Three Months Ended March 31,
	2019		2018
Research and development	$	462	$	431
General and administrative		775		702
Total	$	1,237	$	1,133

Summary of Activity Related to Stock Options

The following table summarizes the activity related to stock options during the three months ended March 31, 2019:

				Weighted
	Number of			Average
	Shares			Exercise Price
Options outstanding at January 1, 2019		3,463,096		$	6.62
Granted		1,532,600			1.24
Exercised		(2,727	)		0.40
Forfeited		(160,080	)		6.25
Options outstanding at March 31, 2019		4,832,889			6.62

Options exercisable at December 31, 2018		1,583,749			5.63

Options exercisable at March 31, 2019		1,593,506			5.77

Commitment and Contingencies (Tables)

3 Months Ended

Mar. 31, 2019

Commitments And Contingencies Disclosure [Abstract]

Operating Leases Included on the Balance Sheet

The Company’s operating leases included on the balance sheet are as follows (in thousands):

	March 31, 2019
Operating lease right-of-use asset	$	925

Liabilities
Current portion of operating lease liabilities	$	499
Operating lease liabilities		1,130
Total operating lease liabilities	$	1,629

Total Future Undiscounted Minimum Lease Payments

Total future undiscounted minimum lease payments were as follows at March 31, 2019 (in thousands):

Year Ending December 31,
2019	$	471
2020		574
2021		496
2022		511
2023		393
Total minimum lease payments	$	2,445

Available-for-Sale Investments (Tables)

3 Months Ended

Mar. 31, 2019

Investments Debt And Equity Securities [Abstract]

Summary of Company's Available-For-Sale Investments

The following table summarizes the Company’s available-for-sale investments (in thousands):

	March 31, 2019
	Amortized		Unrealized		Fair
	Cost		Losses		Value
Commercial paper	$	1,988	$	—	$	1,988
Total available-for-sale investments	$	1,988	$	—	$	1,988

Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2019

Fair Value Disclosures [Abstract]

Summary of Assets Measured at Fair Value

The following tables summarize the fair value of financial assets that are measured at fair value and the classification by level of input within the fair value hierarchy (in thousands):

	March 31, 2019
	Level 1		Level 2		Level 3		Recorded Value
Financial Assets:
Cash and money markets	$	32,950	$	—	$	—	$	32,950
Restricted cash money market		360		—		—		360
Commercial paper		—		1,988		—		1,988
Total financial assets	$	33,310	$	1,988	$	—	$	35,298

	December 31, 2018
	Level 1		Level 2		Level 3		Recorded Value
Financial Assets:
Cash and money markets	$	8,042	$	—	$	—	$	8,042
Restricted cash money market		360		—		—		360
Treasury bills		7,490		—		—		7,490
Commercial paper		—		25,346		—		25,346
Total financial assets	$	15,892	$	25,346	$	—	$	41,238

Net Loss per Share (Tables)

3 Months Ended

Mar. 31, 2019

Earnings Per Share [Abstract]

Potential Common Stock Equivalents Excluded from Computation of Diluted Net Loss per Share

The Company’s potential common stock equivalents that have been excluded from the computation of diluted net loss per share for all periods presented because of their antidilutive effect consisted of the following:

	Three Months Ended March 31,
	2019		2018
Outstanding stock options		4,832,889		3,135,929
Stock purchase warrants		29,796		29,796
		4,862,685		3,165,725

The Company - Additional Information (Details) - USD ($) $ in Millions			3 Months Ended
	Jul. 13, 2017	Jun. 30, 2017	Mar. 31, 2019
Organization Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Entity incorporation date			May 26, 2011
Cash, cash equivalents and short-term investments			$ 34.9
At-the-market sales agreement \| Cowen and Company LLC \| Common Stock
Organization Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Number of shares sold under facility			4,700,000
Net proceeds from issuance of stock			$ 6.6
At-the-market sales agreement \| Cowen and Company LLC \| Common Stock \| Maximum
Organization Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Aggregate offering price, shares	$ 18.5	$ 50.0

Significant Accounting Policies - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Jan. 01, 2019
Significant Accounting Policies [Line Items]
Short-term investments maturity start period	90 days
Short-term investments maturity end period	365 days
Recognition of a right-of use asset	$ 925
Recognition of a lease obligations	$ 1,629
ASU 2016-02
Significant Accounting Policies [Line Items]
Recognition of a right-of use asset		$ 1,000
Recognition of a lease obligations		$ 1,700

Property and Equipment, Net - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Property Plant And Equipment [Line Items]
Property and Equipment, gross	$ 1,217	$ 1,199
Less: Accumulated depreciation	(462)	(409)
Property and equipment, net	755	790
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Property and Equipment, gross	$ 400	382
Estimated Useful Lives (Years)	5 years
Machinery and Equipment
Property Plant And Equipment [Line Items]
Property and Equipment, gross	$ 121	121
Estimated Useful Lives (Years)	5 years
Computer Equipment
Property Plant And Equipment [Line Items]
Property and Equipment, gross	$ 19	19
Estimated Useful Lives (Years)	3 years
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and Equipment, gross	$ 677	$ 677
Estimated Useful Lives (Years)	Lesser of useful life or remaining lease term

Accrued Liabilities - Schedule of Accrued Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Payables And Accruals [Abstract]
Accrued research and development	$ 3,268	$ 1,263
Accrued marketing	366	47
Accrued bonuses	405	1,088
Accrued professional fees	129	63
Accrued vacation	169	103
Accrued interest payable		76
Accrued expense	183	283
Accrued liabilities, current	$ 4,520	$ 2,923

Long-Term Debt - Additional Information (Details) - USD ($)			1 Months Ended	3 Months Ended
	May 14, 2018	Sep. 28, 2016	Sep. 30, 2016	Mar. 31, 2019	Mar. 31, 2018
Debt Instrument [Line Items]
Interest expense on borrowings				$ 225,000	$ 161,000
Accretion of scheduled final payment				46,000	49,000
Accretion of deferred debt issuance costs				15,000	$ 49,000
Second Amended and Restated Loan and Security Agreement
Debt Instrument [Line Items]
Long term debt				$ 10,000,000
Silicon Valley Bank, MidCap Funding XII Trust and MidCap Financial Trust \| First Amended and Restated Loan and Security Agreement
Debt Instrument [Line Items]
Fixed interest rate			7.00%
Variable interest rate			0.50%
Debt instrument, description of variable rate basis				30-day U.S. LIBOR
Line of credit facility, maximum borrowing capacity			$ 15,000,000
Long term debt		$ 8,000,000
Line of credit facility, remaining borrowing capacity				$ 7,000,000
Debt Instrument, Payment Terms				The Company was required to pay accrued interest only on the outstanding $8.0 million balance through December 31, 2017, followed by 30 equal payments of principal and accrued interest.
Final payment during maturity				$ 500,000
Debt instrument, maturity date				Jun. 01, 2020
Repay all the amount outstanding under the loan agreement including fees		$ 5,300,000
Silicon Valley Bank, MidCap Funding XII Trust and MidCap Financial Trust \| First Amended and Restated Loan and Security Agreement \| Final Payment
Debt Instrument [Line Items]
Repay all the amount outstanding under the loan agreement including fees	$ 7,000,000
Silicon Valley Bank, MidCap Funding XII Trust and MidCap Financial Trust \| First Amended and Restated Loan and Security Agreement \| Prepayments Through May 31, 2020
Debt Instrument [Line Items]
Prepayment fee percentage of the original principal amount of the aggregate term loans			2.00%
Silicon Valley Bank, MidCap Funding III Trust and MidCap Financial Trust \| Second Amended and Restated Loan and Security Agreement
Debt Instrument [Line Items]
Fixed interest rate	6.50%
Variable interest rate	1.89%
Debt instrument, description of variable rate basis				30-day U.S. LIBOR
Line of credit facility, maximum borrowing capacity	$ 20,000,000
Long term debt	10,000,000
Debt instrument, maturity date				Oct. 01, 2022
Line of credit facility remaining borrowing capacity not available for withdraw	5,000,000
Final payment during maturity, percentage				5.50%
Silicon Valley Bank, MidCap Funding III Trust and MidCap Financial Trust \| Second Amended and Restated Loan and Security Agreement \| Term C Loan
Debt Instrument [Line Items]
Line of credit facility, remaining borrowing capacity	5,000,000
Silicon Valley Bank, MidCap Funding III Trust and MidCap Financial Trust \| Second Amended and Restated Loan and Security Agreement \| Prepayment Prior to May 14, 2019
Debt Instrument [Line Items]
Prepayment fee percentage of the original principal amount				3.00%
Silicon Valley Bank, MidCap Funding III Trust and MidCap Financial Trust \| Second Amended and Restated Loan and Security Agreement \| Prepayment on or After May 14, 2019 but Prior to October 1, 2022
Debt Instrument [Line Items]
Prepayment fee percentage of the original principal amount				2.00%
Silicon Valley Bank, MidCap Funding III Trust and MidCap Financial Trust \| Second Amended and Restated Loan and Security Agreement, Initial Tranche
Debt Instrument [Line Items]
Long term debt	$ 10,000,000

Long-Term Debt - Scheduled Payments for the Second Amended and Restated Loan and Security Agreement (Details) - Second Amended and Restated Loan and Security Agreement $ in Thousands	Mar. 31, 2019 USD ($)
Debt Instrument [Line Items]
Principal, 2019	$ 556
Principal, 2020	3,333
Principal, 2021	3,333
Principal, 2022	2,778
Principal	10,000
Interest and Final Payment, 2019	635
Interest and Final Payment, 2020	651
Interest and Final Payment, 2021	366
Interest and Final Payment, 2022	638
Interest and Final Payment	2,290
Total, 2019	1,191
Total, 2020	3,984
Total, 2021	3,699
Total, 2022	3,416
Total	$ 12,290

Common Stock - Additional Information (Details) - $ / shares	Mar. 31, 2019	Dec. 31, 2018
Equity [Abstract]
Common stock, shares authorized	100,000,000	100,000,000
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares outstanding	36,782,920	32,119,227

Stock Purchase Warrants - Additional Information (Details) - Convertible Stock Warrant - First Amended and Restated Loan and Security Agreement - $ / shares	1 Months Ended	3 Months Ended
	Sep. 30, 2016	Mar. 31, 2019
Class Of Warrant Or Right [Line Items]
Class of warrant Exercise	$ 10.74
Warrants expiration term	2026-09
Weighted average remaining life of warrants		7 years 6 months
Maximum
Class Of Warrant Or Right [Line Items]
Number of stock that can be purchased by each warrant	29,796

Share-Based Compensation - Summary of Share-based Compensation Expense (Details) - Stock Options - 2011 Stock Incentive Plan, 2016 Equity Incentive Plan - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Share-based compensation expense	$ 1,237	$ 1,133
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Share-based compensation expense	462	431
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Share-based compensation expense	$ 775	$ 702

Share-Based Compensation - Summary of Activity Related to Stock Options (Details) - Stock Options - $ / shares	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares, Options outstanding, Beginning balance	3,463,096
Number of Shares, Granted	1,532,600
Number of Shares, Exercised	(2,727)
Number of Shares, Forfeited	(160,080)
Number of Shares, Options outstanding, Ending balance	4,832,889
Number of Shares, Options exercisable	1,593,506	1,583,749
Weighted Average Exercise Price, Options outstanding, Beginning balance	$ 6.62
Weighted Average Exercise Price, Granted	1.24
Weighted Average Exercise Price, Exercised	0.40
Weighted Average Exercise Price, Forfeited	6.25
Weighted Average Exercise Price, Options outstanding, Ending balance	6.62
Weighted Average Exercise Price, Options exercisable	$ 5.77	$ 5.63

Share-Based Compensation - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
2016 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock purchased	22,287
Share-based compensation expense	$ 9,800	$ 5,000
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation expense related to unvested stock options	$ 10,300,000
Expected to be recognized over a weighted average period	2 years 8 months 12 days

Commitment and Contingencies - Additional Information (Details)	1 Months Ended		3 Months Ended
	Aug. 31, 2018 USD ($) ft²	Nov. 30, 2016 USD ($) ft²	Mar. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)
Commitment And Contingencies [Line Items]
Lessee, operating lease, option to extend, description			The renewal option is not included in the calculation of the right-of-use asset and the lease liabilities as the Company has not yet determined if the leases will be renewed.
Weighted average discount rate			5.30%
Weighted average lease term			2 years 10 months 24 days
Rent expense			$ 100,000	$ 58,000
Cash payments included in operating activities for operating lease liabilities			$ 129,000
GEORGIA
Commitment And Contingencies [Line Items]
Area of office leased \| ft²		20,000
Operating lease agreement term		6 years 6 months
Operating lease agreement renewal option term		5 years
Minimum monthly lease payments		$ 35,145
Percentage of increase per year		3.00%
CALIFORNIA
Commitment And Contingencies [Line Items]
Area of office leased \| ft²	3,500
Operating lease agreement term	2 years
Operating lease agreement renewal option term	1 year
Minimum monthly lease payments	$ 12,775
Percentage of increase per year	3.00%

Commitment and Contingencies - Operating Leases Included on the Balance Sheet (Details) $ in Thousands	Mar. 31, 2019 USD ($)
Commitments And Contingencies Disclosure [Abstract]
Operating lease right-of-use asset	$ 925
Liabilities
Current portion of operating lease liabilities	499
Operating lease liabilities	1,130
Total operating lease liabilities	$ 1,629

Commitment and Contingencies - Total Future Undiscounted Minimum Lease Payments (Details) $ in Thousands	Mar. 31, 2019 USD ($)
Commitments And Contingencies Disclosure [Abstract]
2019	$ 471
2020	574
2021	496
2022	511
2023	393
Total minimum lease payments	$ 2,445

Collaboration Agreements - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2019 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue	$ 45,000
Minimum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Other short-term collaboration agreements performance obligations period	1 month
Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Other short-term collaboration agreements performance obligations period	2 months
Collaboration Agreements
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue	$ 45,000

Available-for-Sale Investments - Summary of Company's Available-For-Sale Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 1,988
Fair Value	1,988	$ 32,835
Commercial Paper
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,988
Fair Value	$ 1,988

Fair Value Measurements - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Short-term investments maturity start period	90 days
Short-term investments maturity end period	365 days
Significant transfers between Levels 1, 2 and 3	$ 0	$ 0

Fair Value Measurements - Summary of Assets Measured at Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Financial Assets:
Total financial assets	$ 35,298	$ 41,238
Treasury Bills
Financial Assets:
Total financial assets		7,490
Commercial Paper
Financial Assets:
Total financial assets	1,988	25,346
Cash and Money Markets
Financial Assets:
Total financial assets	32,950	8,042
Restricted Cash Money Market
Financial Assets:
Total financial assets	360	360
Level 1
Financial Assets:
Total financial assets	33,310	15,892
Level 1 \| Treasury Bills
Financial Assets:
Total financial assets		7,490
Level 1 \| Cash and Money Markets
Financial Assets:
Total financial assets	32,950	8,042
Level 1 \| Restricted Cash Money Market
Financial Assets:
Total financial assets	360	360
Level 2
Financial Assets:
Total financial assets	1,988	25,346
Level 2 \| Commercial Paper
Financial Assets:
Total financial assets	$ 1,988	$ 25,346

Net Loss Per Share - Potential Common Stock Equivalents Excluded from Computation of Diluted Net Loss per Share (Details) - shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	4,862,685	3,165,725
Outstanding Stock Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	4,832,889	3,135,929
Stock Purchase Warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	29,796	29,796