Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Apr. 30, 2018	Jul. 16, 2018	Oct. 31, 2017
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Apr. 30, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY
Trading Symbol	KALV
Entity Registrant Name	KALVISTA PHARMACEUTICALS, INC.
Entity Central Index Key	0001348911
Current Fiscal Year End Date	--04-30
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		10,799,895
Entity Public Float			$ 60,287,969

Consolidated Balance Sheets - USD ($) $ in Thousands	Apr. 30, 2018	Apr. 30, 2017
Current assets:
Cash and cash equivalents	$ 51,055	$ 30,950
Research and development tax credit receivable	6,834	2,250
Grants and other receivables		297
Prepaid expenses and other current assets	1,491	701
Total current assets	59,380	34,198
Other assets	173	50
Property and equipment, net	1,836	97
Total assets	61,389	34,345
Current liabilities:
Accounts payable	1,433	1,153
Accrued expenses	3,087	1,865
Deferred revenue - current portion	18,475
Capital lease liability - current portion	221
Total current liabilities	23,216	3,018
Long-term liabilities:
Deferred revenue - net of current portion	10,862
Capital lease liability - net of current portion	58
Total long-term liabilities	10,920
Commitments and contingencies (Note 8)
Stockholders’ equity:
Common stock, $0.001 par value, 100,000,000 authorized, shares issued and outstanding: 10,799,895 at April 30, 2018 and 9,713,042 at April 30, 2017	11	10
Additional paid-in capital	100,011	89,815
Accumulated deficit	(71,660)	(55,855)
Accumulated other comprehensive loss	(1,109)	(2,643)
Total stockholders’ equity	27,253	31,327
Total liabilities and stockholders’ equity	$ 61,389	$ 34,345

Consolidated Balance Sheets (Parenthetical) - $ / shares	Apr. 30, 2018	Apr. 30, 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	10,799,895	9,713,042
Common stock, shares outstanding	10,799,895	9,713,042

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2016
Income Statement [Abstract]
Revenue	$ 8,394	$ 1,504	$ 2,133
Operating expenses:
Research and development expenses	18,237	12,666	14,661
General and administrative expenses	8,862	11,177	2,653
Total operating expenses	27,099	23,843	17,314
Operating loss	(18,705)	(22,339)	(15,181)
Other income:
Interest income	82	36	50
Foreign currency exchange rate (loss) gain	(1,574)	1,371	1,661
Other income	4,392	2,329	2,034
Total other income	2,900	3,736	3,745
Net loss	(15,805)	(18,603)	(11,436)
Other comprehensive income (loss):
Foreign currency translation adjustments	1,534	(2,568)	(2,240)
Comprehensive loss	$ (14,271)	$ (21,171)	$ (13,676)
Net loss per share attributable to common stockholders, basic and diluted	$ (1.53)	$ (4.47)	$ (26.17)
Weighted average common shares outstanding, basic and diluted	10,321,780	4,646,764	591,298

Consolidated Statements of Changes in Convertible Preferred Shares and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Ordinary Shares [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	KALVISTA PHARMACEUTICALS, INC. [Member]	KALVISTA PHARMACEUTICALS, INC. [Member] Ordinary Shares [Member]	KALVISTA PHARMACEUTICALS, INC. [Member] Common Stock [Member]	KALVISTA PHARMACEUTICALS, INC. [Member] Additional Paid-in Capital [Member]	Series B Convertible Preferred Stock [Member]	Series B Convertible Preferred Stock [Member] KALVISTA PHARMACEUTICALS, INC. [Member]	Series A Convertible Preferred Stock [Member]	Series A Convertible Preferred Stock [Member] KALVISTA PHARMACEUTICALS, INC. [Member]	Convertible Preferred Stock [Member]	Convertible Preferred Stock [Member] KALVISTA PHARMACEUTICALS, INC. [Member]
Balance at Apr. 30, 2015													$ 25,606		$ 25,606
Balance, shares at Apr. 30, 2015													15,900,000		15,900,000
Balance at Apr. 30, 2015	$ (23,555)	$ 2		$ 94	$ (25,816)	$ 2,165
Balance, shares at Apr. 30, 2015		1,302,367
Issuance of convertible preferred stock net of issuance costs											$ 33,002				$ 33,002
Issuance of convertible preferred stock net of issuance costs, shares											8,422,898				8,422,898
Issuance of ordinary shares/ common stock	1	$ 1
Issuance of ordinary shares/ common stock, shares		865,000
Stock-based compensation expense	118			118
Net loss	(11,436)				(11,436)
Foreign currency translation adjustments	(2,240)					(2,240)
Balance at Apr. 30, 2016											$ 33,002		$ 25,606		$ 58,608
Balance, shares at Apr. 30, 2016											8,422,898		15,900,000		24,322,898
Balance at Apr. 30, 2016	(37,112)	$ 3		212	(37,252)	(75)
Balance, shares at Apr. 30, 2016		2,167,367
Issuance of ordinary shares/ common stock	2	$ 2
Issuance of ordinary shares/ common stock, shares		396,719
Transaction, value												$ (33,002)		$ (25,606)		$ (58,608)
Transaction, shares												(8,422,898)		(15,900,000)		(24,322,898)
Transaction, value							$ 89,214	$ (5)	$ 10	$ 89,209
Transaction, shares								(2,564,086)	9,713,042
Stock-based compensation expense	394			394
Net loss	(18,603)				(18,603)
Foreign currency translation adjustments	(2,568)					(2,568)
Balance at Apr. 30, 2017	31,327		$ 10	89,815	(55,855)	(2,643)
Balance, shares at Apr. 30, 2017			9,713,042
Issuance of ordinary shares/ common stock	9,101		$ 1	9,100
Issuance of ordinary shares/ common stock, shares			1,070,589
Issuance of common stock from stock options exercised	$ 36			36
Issuance of common stock from stock options exercised, shares	16,264		16,264
Stock-based compensation expense	$ 1,060			1,060
Net loss	(15,805)				(15,805)
Foreign currency translation adjustments	1,534					1,534
Balance at Apr. 30, 2018	$ 27,253		$ 11	$ 100,011	$ (71,660)	$ (1,109)
Balance, shares at Apr. 30, 2018			10,799,895

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2016
Cash flows from operating activities:
Net loss	$ (15,805)	$ (18,603)	$ (11,436)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	180	40	33
Stock-based compensation expense	1,060	394	118
Foreign currency remeasurement loss	(651)	(1,371)	(1,661)
Changes in operating assets and liabilities, net of changes from business acquired:
Research and development tax credit receivable	(4,256)	(600)	(1,148)
Grants and other receivables	319	29	(137)
Prepaid expenses and other current assets	(746)	(81)	(475)
Other assets	(123)
Accounts payable	217	(1,599)	374
Accrued expenses	1,132	(1,931)	1,176
Deferred revenue	29,231
Net cash provided by (used in) operating activities	10,558	(23,722)	(13,156)
Cash flows from investing activities:
Cash acquired in transaction		34,139
Acquisition of property and equipment	(1,427)	(74)	(11)
Net cash provided by (used in) investing activities	(1,427)	34,065	(11)
Cash flows from financing activities:
Capital lease principal payments	(151)
Proceeds from issuance of common stock	9,137	2	1
Proceeds from issuance of Series B Preferred Stock, net of issuance costs			33,002
Net cash provided by financing activities	8,986	2	33,003
Effect of exchange rate changes on cash and cash equivalents	1,988	(1,159)	(598)
Net increase in cash and cash equivalents	20,105	9,186	19,238
Cash and cash equivalents, beginning year	30,950	21,764	2,526
Cash and cash equivalents, end of year	51,055	30,950	$ 21,764
Supplemental disclosures of cash flow information:
Conversion of preferred stock and ordinary shares to common stock		$ 58,613
Capital leases	513
Acquisition of property and equipment in accounts payable	$ 291

Description of Business, Basis of Presentation and Going Concern	12 Months Ended
	Apr. 30, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Description of Business, Basis of Presentation and Going Concern	Note 1. Description of Business, Basis of Presentation and Going Concern KalVista Pharmaceuticals, Inc. (“KalVista” or the “Company”) is a clinical stage pharmaceutical company focused on the discovery, development and commercialization of small molecule protease inhibitors for diseases with significant unmet need. The Company’s first product candidates are inhibitors of plasma kallikrein being developed for two indications: hereditary angioedema (“HAE”) and diabetic macular edema (“DME”). The Company applies its insights into the chemistry of proteases and, with current programs, the biology of the plasma kallikrein system, to develop small molecule inhibitors with high selectivity, potency and bioavailability that it believes will make them successful treatments for disease. KalVista has created a structurally diverse portfolio of oral plasma kallikrein inhibitors and advanced multiple drug candidates into Phase 1 clinical trials for HAE in order to create best-in-class oral therapies. In December 2017, the Company initiated a first-in-human study of KVD900, the next candidate from its HAE portfolio to commence clinical testing. Based upon the results observed to date in that study, the Company has determined to advance KVD900 into later stage clinical trials as a potential on-demand therapy for acute HAE attacks. In the case of DME, the Company is initially developing a plasma kallikrein inhibitor which is administered directly into the eye and anticipates ultimate development of orally delivered drugs. Also in December 2017 KalVista commenced a Phase 2 clinical trial of KVD001, the Company’s most advanced DME drug candidate, that it anticipates will complete in the second half of 2019. In October 2017, the Company’s wholly-owned, U.K. based subsidiary KalVista Pharmaceuticals Limited (“KalVista Limited) and Merck Sharp & Dohme Corp. (“Merck”) entered into an option agreement (the “Option Agreement”) under which the Company granted to Merck an option to acquire KVD001 through a period following completion of a Phase 2 clinical trial. The Company also granted to Merck a similar option to acquire investigational orally delivered molecules for DME (the “Oral DME Compounds”) that the Company will continue to develop as part of its ongoing research and development activities, through a period following the completion of a Phase 2 clinical trial. Under the terms of the Option Agreement, Merck paid to the Company a non-refundable upfront fee of $37 million in November 2017. See Note 5 for further discussion of the arrangement with Merck. The Company’s headquarters is located in Cambridge, Massachusetts, with research activities located in Porton Down, United Kingdom and Boston, Massachusetts. The Company has devoted substantially all of its efforts to research and development, including clinical trials of its product candidates. The Company has not completed the development of any product candidates. Pharmaceutical drug product candidates, like those being developed by the Company, require approvals from the U.S. Food and Drug Administration (“FDA”) or foreign regulatory agencies prior to commercial sales. There can be no assurance that any product candidates will receive the necessary approvals and any failure to receive approval or delay in approval may have a material adverse impact on the Company’s business and financial results. The Company has not yet commenced commercial operations. The Company is subject to a number of risks and uncertainties similar to those of other life science companies developing new products, including, among others, the risks related to the necessity to obtain adequate additional financing, to successfully develop product candidates, to obtain regulatory approval of product candidates, to comply with government regulations, to successfully commercialize its potential products, to the protection of proprietary technology and to the dependence on key individuals. The Company has funded its operations primarily through the issuance of preferred stock and common stock, the share purchase transaction with Carbylan Therapeutics, Inc. (“Carbylan”), the Option Agreement and grant income. As of April 30, 2018, the Company had an accumulated deficit of $71.7 million and cash and cash equivalents totaling $51.1 million. The Company’s working capital, primarily cash, is anticipated to fund the Company’s operations for at least 12 months beyond the date of issuance of the consolidated financial statements. Accordingly, the consolidated financial statements have been prepared on a going concern basis. The Company will need to expend substantial resources for research and development, including costs associated with the clinical testing of its product candidates and will need to obtain additional financing to fund its operations and to conduct trials for its product candidates. The Company will seek to finance future cash needs through equity offerings, future grants, corporate partnerships and product sales. The Company has never been profitable and has incurred significant operating losses in each year since inception. Cash requirements may vary materially from those now planned because of changes in the Company’s focus and direction of its research and development programs, competitive and technical advances, patent developments, regulatory changes or other developments. Additional financing will be required to continue operations after the Company exhausts its current cash resources and to continue its long-term plans for clinical trials and new product development. There can be no assurance that any such financing can be obtained by the Company, or if obtained, what the terms thereof may be, or that any amount that the Company is able to raise will be adequate to support the Company’s working capital requirements until it achieves profitable operations. If adequate additional working capital is not secured when needed, the Company may be required to make reductions in spending, extend payment terms with suppliers, liquidate assets where possible and/or suspend or curtail planned research programs. Any of these actions could materially harm the Company’s business and prospects.

Summary of Significant Accounting Policies

12 Months Ended

Apr. 30, 2018

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

Note 2. Summary of Significant Accounting Policies

Principles of consolidation: The accompanying consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation.

Use of estimates: The preparation of consolidated 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 consolidated financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from these estimates.

Foreign currency: The functional currency of the Company’s foreign subsidiary is the Great Britain Pound Sterling. Assets and liabilities of the foreign subsidiary are translated using the exchange rate existing on each respective balance sheet date. Revenues and expenses are translated using average exchange rates prevailing throughout the year. The translation adjustments resulting from this process are included as the only component of the accumulated other comprehensive loss. In addition, the Company’s foreign subsidiary engages in transactions and holds balances denominated and settled in currencies other than the functional currency, and transaction gains or losses are recorded in the consolidated statement of operations.

Segment Reporting: The Chief Operating Decision Maker, the CEO, manages the Company’s operations as a single operating segment for the purposes of assessing performance and making operating decisions.

Cash and cash equivalents: Cash and cash equivalents consist of bank deposits and money market accounts. Cash equivalents are carried at cost which approximates fair value due to their short-term nature. The Company considers all highly liquid investments with an original maturity of 90 days or less to be cash equivalents.

The Company maintains its cash and cash equivalent balances with financial institutions that management believes are of high credit quality. The Company’s cash and cash equivalent accounts at times may exceed federally insured limits. The Company has not experienced any losses in such accounts. The Company believes it is not exposed to any significant credit risk of cash and cash equivalents.

Research and development tax credit receivable: The research and development tax credit receivable consists of research and development expenses that have been claimed as research and development tax credits in accordance with the relevant U.K. tax legislation. These refundable tax credits are payable to the Company in cash and are carried on the consolidated balance sheet at the amount claimed and expected to be received from the U.K. government.

Property and equipment: Property and equipment are stated at cost less accumulated depreciation. Expenditures for repairs and maintenance are charged to expense as incurred. Upon retirement or sale, the costs of the assets disposed of and the related accumulated depreciation are eliminated from the accounts and any resulting gain or loss is reflected in the statement of operations. Depreciation is provided using the straight-line method over the estimated useful lives of the assets, which are as follows:

Asset Classification		Estimated Useful Life
Machinery and equipment		1-5 Years
Computer equipment		3-4 Years
Motor vehicles		4 Years
Leasehold improvements		5 Years or term of lease, if shorter

The Company assesses the impairment of long-lived assets whenever events or changes in circumstances indicate that the carrying value of such assets, or asset groups, may not be recoverable. Whenever events or changes in circumstances suggest that the carrying amount of long-lived assets may not be recoverable, the future undiscounted cash flows expected to be generated by the asset, or asset groups, from its use or eventual disposition is estimated. If the sum of the expected future undiscounted cash flows is less than the carrying amount of those assets, or asset groups, an impairment loss is recognized based on the excess of the carrying amount over the fair value of the assets, or asset groups.

Revenue recognition: The Company recognizes revenue from research and development arrangements and grant income. Revenue is realized or realizable and earned when all of the following criteria are met: (i) persuasive evidence of an arrangement exists; (ii) delivery has occurred or services have been rendered; (iii) the seller’s price to the buyer is fixed or determinable; and (iv) collectability is reasonably assured.

Grant income is received for the development and commercialization of product candidates through sponsored research arrangements with non-profit organizations and from federal research and development grant programs. Revenue is recognized as qualifying research and development costs are incurred. The existing grant program is sponsored by the U.K. government and is substantially complete, with no significant further reimbursements anticipated.

For arrangements that involve the delivery of more than one element, such as the Option Agreement, each product, service and/or right to use assets is evaluated to determine whether it qualifies as a separate unit of accounting. This determination is based on whether the deliverable has “stand-alone value” to the customer. The consideration that is fixed or determinable is then allocated to each separate unit of accounting based on the relative selling price of each deliverable. The estimated selling price of each deliverable is determined using the following hierarchy of values: (i) vendor-specific objective evidence of fair value, (ii) third-party evidence of selling price and (iii) best estimate of selling price (“BESP”). The BESP reflects the Company’s best estimate of what the selling price would be if the deliverable was regularly sold by the Company on a stand-alone basis. The consideration allocated to each unit of accounting is recognized as the related goods or services are delivered, limited to the consideration that is not contingent upon future deliverables. Analyzing the arrangement to identify deliverables requires the use of judgment, and each deliverable may be an obligation to deliver services, a right or license to use an asset, or another performance obligation.

Research and development: Research and development costs are expensed as incurred and include, but are not limited to:

•

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

•

Costs associated with preclinical and development activities;

•

Costs associated with regulatory operations.

Income taxes: The Company uses the asset and liability method for accounting for income taxes. Under this method, deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective income tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The Company evaluates the realizability of its deferred tax assets and establishes a valuation allowance when it is more likely than not that all or a portion of deferred tax assets will not be realized. The Company has provided a full valuation allowance on its deferred tax assets.

Relative to accounting for uncertainties in tax positions, the Company recognizes the tax benefit of tax positions to the extent that the benefit will more likely than not be realized. The determination as to whether the tax benefit will more likely than not be realized is based upon the technical merits of the tax position as well as consideration of the available facts and circumstances. For those tax positions where it is more likely than not that a tax benefit will be sustained, the Company records the largest amount of tax benefit with a greater than 50% likelihood of being realized upon ultimate settlement with a taxing authority having full knowledge of all relevant information. For those income tax positions where it is not more likely than not that a tax benefit will be sustained, the Company does not recognize a tax benefit in the financial statements.

The Company recognizes interest and penalties related to uncertain tax positions, if any, as a component of income tax expense. As the Company has no uncertain tax positions, there were no interest or penalties charges recognized in the statement of operations for any years.

Stock based compensation: The Company accounts for stock based compensation arrangements at fair value. The fair value is recognized over the period during which the recipient is required to provide services (usually the vesting period), on a straight-line basis.

Net Loss per Share Attributable to Common Shareholders: Basic and diluted net loss per share is presented in conformity with the two-class method required for participating securities. Under the two-class method, basic net loss per share is computed by dividing the net loss attributable to common stockholders by the weighted average number of common shares outstanding during the period. Net loss attributable to common stockholders is determined by allocating undistributed earnings between holders of common and convertible preferred shares, based on the contractual dividend rights contained in the preferred share agreement. Where there is an undistributed loss, no amount is allocated to the convertible preferred shares. Diluted net loss per share is computed by dividing net loss by the sum of the weighted average number of common stock and the number of dilutive potential common stock equivalents outstanding during the period. Potential dilutive common share equivalents consist of the incremental common shares issuable upon the exercise of vested share options or the conversion of preferred stock.

Potential dilutive common share equivalents consist of:

	April 30,
	2018		2017		2016
Preferred stock		—		—		24,322,898
Stock options		388,366		148,469		76,643

In computing diluted earnings per share, common stock equivalents are not considered in periods in which a net loss is reported, as the inclusion of the common stock equivalents would be anti-dilutive. As a result, there is no difference between the Company’s basic and diluted loss per share in the periods presented (in thousands, except share and per share amounts):

Basic and diluted net loss per share	April 30,
	2018			2017			2016
Net loss	$	(15,805	)	$	(18,603	)	$	(11,436	)
Less: dividend on Series A		—			(935	)		(1,918	)
Less: dividend on Series B		—			(1,237	)		(2,121	)
Loss available to common stockholders		(15,805	)		(20,775	)		(15,475	)
Weighted average common shares, basic and diluted		10,321,780			4,646,764			591,298
Net loss per share, basic and diluted	$	(1.53	)	$	(4.47	)	$	(26.17	)

The weighted average shares outstanding, reported loss per share and potential dilutive common share equivalents for the periods prior to November 21, 2016, the date of the Carbylan transaction, have been retrospectively adjusted to reflect historical weighted-average number of common shares outstanding multiplied by the exchange ratio established in the share purchase agreement.

Fair value measurement: The Company classifies fair value measurements using a three-level hierarchy that prioritizes the inputs used to measure fair value. This hierarchy requires entities to maximize the use of observable inputs and minimize the use of unobservable inputs. The three levels of inputs used to measure fair value are as follows: Level 1, quoted market prices in active markets for identical assets or liabilities; Level 2, observable inputs other than quoted market prices included in Level 1, such as quoted market prices for markets that are not active or other inputs that are observable or can be corroborated by observable market data; and Level 3, unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities, including certain pricing models, discounted cash flow methodologies and similar techniques that use significant unobservable inputs.

The Company’s financial instruments as of April 30, 2018 and 2017 consisted primarily of cash and cash equivalents, grants receivable, capital lease obligations and accounts payable. The carrying amount of these assets and liabilities approximate fair value given the short term maturity of these instruments.

Correction: The statements of operations and comprehensive loss for the year ended April 30, 2016 was restated in the prior year to correct errors in the foreign currency translation adjustments which were reported as a gain rather than a loss and to correct the resulting summation of comprehensive loss. As a result of the correction of these errors, the total comprehensive loss for the year ended April 30, 2016 increased from a loss of $9,196,000 to a loss of $13,676,000. There is no impact on the Company’s previously reported net loss, the balance sheet, the statement of changes in convertible preferred shares and stockholders’ equity (deficit) or the statement of cash flows for any period.

Recently issued accounting pronouncements not yet adopted: In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards update (“ASU”) 2014-09, “Revenue from Contracts with Customers,” requiring an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers. The updated standard will replace most existing revenue recognition guidance in US GAAP when it becomes effective. The Company will adopt the updated standard in the first quarter of fiscal 2019 using the modified retrospective method of adoption. The adoption of this standard is not expected to have a material impact on the consolidated financial statements.

In February 2016, the FASB issued new lease accounting guidance in ASU No. 2016-02, “Leases” (Topic 842). Under the new guidance, lessees will be required to recognize for all leases (with the exception of short-term leases) at the commencement date: (1) a lease liability, which is a lessee’s obligation to make lease payments arising from a lease, measured on a discounted basis; and (2) a right-of-use asset, which is an asset that represents the lessee’s right to use, or control the use of, a specified asset for the lease term. The new lease guidance is effective for the Company beginning May 1, 2019. The Company is assessing the impact that adoption of this new guidance will have on the consolidated financial statements, but expects to recognize a material lease obligation and right of use asset. See additional discussion of the Company’s lease obligation included in Note 8.

Recently adopted accounting pronouncements

In March 2016, the FASB issued ASU No. 2016-09, Compensation –Stock Compensation (Topic 718) (“ASU 2016-09”) to require changes to several areas of employee share-based payment accounting in an effort to simplify share-based reporting. The update revises requirements in the following areas: minimum statutory withholding, accounting for income taxes and forfeitures. The Company adopted this standard effective May 1, 2017, and is now accounting for forfeitures as incurred. The adoption of this standard did not have a material impact on the consolidated financial statements.

Property and Equipment

12 Months Ended

Apr. 30, 2018

Property Plant And Equipment [Abstract]

Property and Equipment

Note 3. Property and Equipment

At April 30, 2018 and 2017, property and equipment consisted of (in thousands):

	2018			2017
Laboratory equipment	$	1,277		$	373
Office equipment		33			31
Furniture & fixtures		76			6
Leasehold improvements		1,005			—
		2,391			410
Less accumulated depreciation		(555	)		(313	)
	$	1,836		$	97

For the years ended April 30, 2018, 2017, and 2016, depreciation expense was $180,000, $40,000 and $33,000, respectively.

Accrued Expenses

12 Months Ended

Apr. 30, 2018

Payables And Accruals [Abstract]

Accrued Expenses

Note 4. Accrued Expenses

At April 30, 2018 and 2017, accrued expenses consisted of (in thousands):

	2018		2017
Accrued research expense	$	1,192	$	348
Accrued compensation		1,393		1,300
Accrued professional fees		164		146
Other accrued expenses		338		71
	$	3,087	$	1,865

Merck Arrangement	12 Months Ended
Merck Arrangement	Apr. 30, 2018
License And Collaboration Arrangements [Abstract]
Merck Arrangement	Note 5. Merck Arrangement On October 6, 2017, the Company’s wholly-owned U.K. based subsidiary KalVista Pharmaceuticals Limited (“KalVista Limited) and Merck Sharp & Dohme Corp. (“Merck”) entered into an option agreement (the “Option Agreement”). The Company is the guarantor of KalVista Limited’s obligations under the Option Agreement. Under the terms of the Option Agreement, the Company, through KalVista Limited, has granted to Merck an option to acquire KVD001 through a period following completion of a Phase 2 clinical trial. The Company, through KalVista Limited, has also granted to Merck a similar option to acquire investigational orally delivered molecules for DME that the Company will continue to develop as part of its ongoing research and development activities, through a period following the completion of a Phase 2 clinical trial. The Company, through KalVista Limited, also granted to Merck a non-exclusive license to use the compounds solely for research purposes, and is required to use its diligent efforts to develop the two compounds through the completion of Phase 2 clinical trials. The Company will fund and retain control over the planned Phase 2 clinical trial of KVD001 as well as development of the investigational oral DME compounds through Phase 2 clinical trials unless Merck determines to exercise its options earlier, at which point Merck will take responsibility for all development and commercialization activities for the compounds. The Company’s development efforts under the Option Agreement are governed by a joint steering committee consisting of equal representatives from the Company and Merck. Under the terms of the Option Agreement, Merck paid a non-refundable upfront fee of $37 million to KalVista Limited in November 2017. If Merck exercises both options under the Option Agreement, KalVista Limited could receive up to an additional $715 million composed of option exercise payments and clinical, regulatory, and sales-based milestone payments. In addition, the Company is eligible for tiered royalties on global net sales ranging from mid-single digits to double digit percentages. Merck may terminate the Option Agreement at any time upon written notice to the Company. KalVista Limited may terminate the Option Agreement in the event of Merck’s material breach of the Option Agreement, subject to cure. Concurrent with the Option Agreement, the Company and Merck also entered into a stock purchase agreement (the “Stock Purchase Agreement”) pursuant to which Merck paid approximately $9.1 million to purchase 1,070,589 new shares of the Company’s common stock at a price of $8.50 per share. The Company determined that the Option Agreement and the Stock Purchase Agreement were negotiated and executed contemporaneously, and therefore should be combined as one arrangement for accounting purposes. The Company evaluated the arrangement in accordance with the provisions of ASC 605-25. The Company determined that the arrangement contains the following deliverables: (i) a non-exclusive license to use the two compounds solely for research purposes, (ii) research and development services related to the development of KVD001 through completion of a Phase 2 clinical trial, (iii) research and development services related to the development of the Oral DME Compounds, and (iv) unregistered shares of the Company’s common stock. The Company has determined that Merck’s options to acquire KVD001 and the Oral DME Compounds are substantive options. Merck is not contractually obligated to exercise the options. The Company has determined that Merck’s options to acquire KVD001 and the Oral DME Compounds are not priced at a significant and incremental discount. Consequently, the Company determined that Merck’s options are not deliverables in the arrangement. The Company further determined that the research license granted did not have standalone value from the respective research and development services, as the license could not be used on its own by Merck for its intended purpose of developing and commercializing KVD001 and the Oral DME Compounds on a standalone basis. As a result, the research license has been combined with the respective research and development services for KVD001 and the Oral DME Compounds as two units of accounting (the “KVD001 Unit of Accounting” and the “Oral DME Unit of Accounting”). The Company has concluded that the common stock deliverable identified at the inception of the arrangement has standalone value from the other deliverables and therefore represents a separate unit of accounting (the “Common Stock Unit of Accounting”). Therefore, the Company has identified three units of accounting under the arrangement as follows: (i) the KVD001 Unit of Accounting, (ii) the Oral DME Unit of Accounting, and (iii) the Common Stock Unit of Accounting. Allocable arrangement consideration at inception of the arrangement is comprised of the non-refundable up-front payment of $37.0 million and the payment for the common stock of $9.1 million. The Company allocated the $9.1 million payment to the common stock, as this represented the fair value of the shares issued based on arms-length negotiations between the Company and Merck. The amount allocated to the common stock is recorded to stockholders’ equity at the date of issuance. The Company allocated the remaining allocable consideration of $37.0 million to the remaining units of accounting using the relative-selling price method. The Company determined that neither vendor-specific objective evidence or third-party evidence is available for any of the units of accounting identified at arrangement inception. Accordingly, the selling price of each unit of accounting was developed using management’s best estimate of selling price. The Company developed the Best Estimate of Selling Price (“BESP”) for the KVD001 Unit of Accounting and Oral DME Unit of Accounting by applying an analysis of discounted cash flows and the allocable arrangement consideration was allocated among the separate units of accounting using the relative selling price method. The amount allocated to each Unit of Accounting will be recognized as revenue on a proportional performance basis. For the fiscal year ended April 30, 2018, the Company recognized approximately $8.0 million of revenue with respect to the arrangement with Merck. As of April 30, 2018, deferred revenue on the consolidated balance sheet is $29.3 million.

Grant Income	12 Months Ended
Grant Income	Apr. 30, 2018
Revenues [Abstract]
Grant Income	Note 6. Grant Income Grant income is primarily recognized through an agreement with the Technology Strategy Board (“TSB”), a United Kingdom government organization. The Company recognizes revenue for reimbursements of research and development costs as the services are performed up to an agreed upon threshold. The Company records these reimbursements as revenue and not as a reduction of research and development expenses, as the Company has the risks and rewards as the principal in the research and development activities. Any services performed and not yet collected upon are shown as a receivable. During years ended April 30, 2018, 2017 and 2016, revenue recognized through the TSB grant amounted to $0.4 million, $1.2 million and $1.8 million, respectively. As of April 30, 2018, the development activities related to the TSB grant have been completed and the Company does not anticipate any further reimbursements from this grant. The Company evaluates the terms of sponsored research agreement grants and federal grants to assess the Company’s obligations and if the Company’s obligations are satisfied by the passage of time, revenue is recognized as described above. For grants with refund provisions, the Company reviews the grant to determine the likelihood of repayment. If the likelihood of repayment of the grant is determined to be remote, the grant is recognized as revenue. If the probability of repayment is determined to be more than remote, the Company records the grant as a deferred revenue liability, until such time that the grant requirements have been satisfied.

Stock-Based Compensation

12 Months Ended

Apr. 30, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation

Note 7. Stock-Based Compensation

The Company has three plans that provide for equity-based compensation. There are two legacy plan that were maintained by Carbylan and KalVista Limited and for which no further grants are to be made. Under the 2017 Equity Incentive Plan (“2017 Plan”), 1,712,287 shares of the Company’s common stock are reserved for issuance upon exercise of stock options. As of April 30, 2018, 1,076,367 stock options remain available for grant under the 2017 Plan.

Initial awards generally vest 25% after one year and then ratably on a monthly basis over the next three years. Recurring grants typically vest on a monthly basis over four years. Stock option grants expire after ten years.

The Company recognizes stock-based compensation expense over the requisite service period based on the grant date fair value of the award. The Company has elected to use the Black-Scholes option pricing model to determine the fair value of awards granted. The determination of the fair value of stock-based awards utilizing the Black-Scholes model is affected by the share price and a number of assumptions, including expected volatility, expected life, risk-free interest rate and expected dividends. Due to insufficient history of the Company’s stock price, the stock-price volatility assumption is based on the historical volatility of a peer group of publicly traded companies. The expected life of the awards is estimated based on the simplified method. The risk-free interest rate assumption is based on observed interest rates appropriate for the terms of the awards. The dividend yield assumption is based on history and expectation of paying no dividends. Forfeitures have not been material in the periods presented.

The fair value of the share-based awards was measured with the following weighted-average assumptions for the fiscal years ended April 30:

	2018	2017	2016
Risk-free interest rate	1.94%	2.08%	1.38%
Expected life of the options	6.25 years	6.25 years	6.25 years
Expected volatility of the underlying stock	76.9%	82.3%	80.9%
Expected dividend rate	0%	0%	0%

Stock-based compensation was reflected in the Company’s consolidated statement of operations and comprehensive loss as follows (in thousands):

	Year ended April 30,
	2018		2017		2016
Research and development	$	320	$	143	$	118
General and administrative		740		251		—
Total stock-based compensation expense	$	1,060	$	394	$	118

A summary of option activity for the year ended April 30, 2018 and changes during the years then ended is presented below:

	Shares			Weighted Average Exercise Price		Weighted Average Remaining Contractual Life		Aggregate Intrinsic Value
Outstanding at May 1, 2017		537,768		$	4.82		9.05	$	1,631
Exercised		(16,264	)		2.13
Granted		409,320			7.10
Cancelled		(12,130	)
Outstanding at April 30, 2018		918,694		$	5.87		8.51	$	3,465
Exercisable at April 30, 2018		388,366		$	4.57		8.02	$	1,967
Vested and expected to vest at April 30, 2018		918,694		$	5.87		8.51	$	3,465

The weighted-average grant date fair value of stock options granted during the years ended, April 30, 2018, 2017, and 2016 was $4.87, $5.68 and $1.41, respectively.

As of April 30, 2018, there was $2.5 million of unrecognized compensation expense related to unvested awards, which is expected to be recognized over a weighted-average period of 2.55 years

Commitments and Contingencies

12 Months Ended

Apr. 30, 2018

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

Note 8. Commitments and Contingencies

Clinical Studies: The Company enters into contractual agreements with contract research organizations in connection with preclinical and toxicology studies and clinical trials. Amounts due under these agreements are invoiced to the Company on predetermined schedules during the course of the toxicology studies and clinical trials and are not refundable regardless of the outcome. The Company has a contractual obligation related to the expected future costs to be incurred to complete the ongoing toxicology studies and clinical trials. The remaining commitment, which has cancellation provisions, totals $8.9 million at April 30, 2018.

Lease commitments: The Company is party to several operating leases for office and laboratory space as well as certain lab equipment. Rent expense was $0.6 million, $0.5 million and $0.1 million for the years ended April 30, 2018, 2017, 2016, respectively, and is reflected in general and administrative expenses and research and development expenses as determined by the underlying activities.

Future minimum payments under these leases as of April 30, 2018 are as follows (in thousands):

	Capital			Operating
Year ended April 30:	Leases			Leases
2019	$	229		$	331
2020		58			329
2021		—			332
2022		—			335
2023 and thereafter					746
Total minimum lease payments		287		$	2,073
Less amounts representing interest		(8	)
Present value of minimum payments		279
Current portion		(221	)
Long-term portion	$	58

Indemnification: In the normal course of business, the Company enters into contracts and agreements that contain a variety of representations and warranties and provide for general indemnification. The Company’s exposure under these agreements is unknown because it involves future claims that may be made against the Company but have not yet been made. To date, the Company has not paid any claims or been required to defend any action related to its indemnification obligations. However, the Company may record charges in the future as a result of these indemnification obligations. No amounts associated with such indemnifications have been recorded to date.

Contingencies: From time to time, the Company may have certain contingent liabilities that arise in the ordinary course of business activities. The Company accrues a liability for such matters when it is probable that future expenditures will be made and such expenditures can be reasonably estimated. There were no contingent liabilities requiring accrual at April 30, 2018 and 2017.

As a result of the terms of grant income received in prior years, upon successful regulatory approval and following the first commercial sale of certain products, the Company will be required to pay royalty fees of up to $1 million within 90 days of the first commercial sale of the product subject to certain caps and follow on payments depending upon commercial success and type of product. Given the stage of development of the current pipeline of products it is not possible to predict with certainty the amount or timing of any such liability.

Income Taxes

12 Months Ended

Apr. 30, 2018

Income Tax Disclosure [Abstract]

Income Taxes

Note 9. Income Taxes

The Company has incurred net losses since inception and, consequently, has not recorded any U.S. Federal and state income tax expense or benefit for the years presented. The Company files tax returns in the United Kingdom as well as U.S. Federal and various state tax returns. Tax years 2018 and 2017 in the U.K. subsidiary remain open to examination by the Her Majesty’s Revenue and Customs (“HMRC”). Further, HMRC will be able to open an inquiry under the ‘discovery assessment’ for the 2014 tax year until April 30, 2018 if HMRC discovers facts which were not disclosed or readily inferable from the tax returns or accounts. The U.S. returns are open for all tax years since inception. The Company is not currently under examination in any jurisdiction for any tax years.

The components of the Company’s loss before income taxes for the years ended April 30 consisted of the following:

	2018			2017			2016
Domestic	$	(4,020	)	$	(2,110	)	$	—
Foreign		(11,785	)		(16,493	)		(11,436	)
	$	(15,805	)	$	(18,603	)	$	(11,436	)

A reconciliation between the effective tax rates and statutory rates for the years ended April 30, is as follows:

	2018			2017			2016
Income tax benefit at U.S. federal statutory rate		30.40	%		34.00	%		34.00	%
Foreign rate differential		(4.26	)%		(11.72	)%		(14.00	)%
Nondeductible expenses		(16.34	)%		(9.16	)%		(6.85	)%
Other		(4.52	)%		(1.29	)%		—
Effect of change in tax rates		(3.61	)%		—			—
Valuation allowance		(1.67	)%		(11.83	)%		(13.15	)%
		0.00	%		0.00	%		0.00	%

The Company has net operating loss carry forwards available to offset future taxable income for federal and state income tax purposes. The ability to utilize the Company’s domestic net operating losses is limited due to changes in ownership as defined by Section 382 of the Internal Revenue Code (the “Code”). Under the provisions of Sections 382 and 383 of the Code, a change of control, as defined in the Code, imposes an annual limitation on the amount of the Company’s net operating loss and tax credit carryforwards, and other tax attributes that can be used to reduce future tax liabilities. The Company determined that an ownership change occurred as a result of the Company’s transaction in November 2016. As a result of this ownership change, the Company’s U.S. federal and California NOL carryforwards may be limited to the extent of recognizing any previously unrecognized built-in gains of Carbylan as of November 2016.

The tax effect of significant temporary differences representing deferred tax assets and liabilities as of April 30, 2018 and 2017 is as follows (in thousands):

	2018			2017
Net operating loss (“NOL”) carryforwards	$	6,596		$	5,602
Other		240			282
Valuation allowance		(6,836	)		(5,884	)
Net deferred tax asset	$	—		$	—

Management of the Company has evaluated the positive and negative evidence bearing upon the realizability of its deferred tax assets, which are comprised principally of NOL carryforwards. As a result of the fact that the Company has incurred tax losses from inception, management has determined that it is more likely than not that the Company will not recognize the benefits of net deferred tax assets and, as a result, a full valuation allowance has been established against its net deferred tax assets as of April 30, 2018 and 2017. During the years ended April 30, 2018, 2017, and 2016 the valuation allowance changed by $1.0 million, $3.0 million and $0.4 million, respectively. Realization of deferred tax assets is dependent upon the generation of future taxable income. As of April 30, 2018, the Company had NOL carryforwards for federal income tax purposes of approximately $4.6 million that begin to expire in 2036, NOL carryforwards for state income taxes of $3.4 million that begin to expire in 2036 and NOL carryforwards for U.K. income taxes of $29.2 million that do not expire.

In December 2017, the Tax Cuts and Jobs Act (“TCJA”) was signed into law. Among other things, the TCJA permanently lowers the corporate federal income tax rate to 21% from the existing maximum rate of 35%, effective for tax years including or commencing January 1, 2018. As a result of the reduction of the corporate federal income tax rate to 21%, U.S. GAAP requires companies to revalue their deferred tax assets and deferred tax liabilities as of the date of enactment, with the resulting tax effects accounted for in the reporting period of enactment. This revaluation resulted in a reduction of the Company’s deferred tax assets of $578,000 and a corresponding reduction in the valuation allowance. As a result, there was no impact on our consolidated statements of operations from the reduction in tax rate. The other provisions of the TCJA did not have a material impact on the consolidated financial statements.

The Company recognizes the financial statement effects of a tax position when it becomes more likely than not, based upon the technical merits, that the position will be sustained upon examination. The Company has no unrecognized tax benefits as of April 30, 2018 and 2017, respectively. The Company does not expect any material changes in the next 12 months in unrecognized tax benefits. The Company has not recognized interest and penalties related to uncertain tax positions.

Unaudited Quarterly Financial Information

12 Months Ended

Apr. 30, 2018

Quarterly Financial Information Disclosure [Abstract]

Unaudited Quarterly Financial Information

Note 12. Unaudited Quarterly Financial Information (in thousands):

Fiscal year 2018	Quarter ended July 31, 2017			Quarter ended October 31, 2017			Quarter ended January 31, 2018			Quarter ended April 30, 2018
Revenue	$	96		$	1,127		$	2,331		$	4,840
Operating expenses		5,549			7,064			6,677			7,809
Net loss		(4,928	)		(4,986	)		(5,234	)		(657	)
Net loss per share	$	(0.51	)	$	(0.50	)	$	(0.49	)	$	(0.06	)

Fiscal year 2017	Quarter ended July 31, 2016			Quarter ended October 31, 2016			Quarter ended January 31, 2017			Quarter ended April 30, 2017
Revenue	$	975		$	197		$	248		$	114
Operating expenses		6,095			4,223			8,365			5,200
Net loss		(3,436	)		(3,297	)		(7,644	)		(4,202	)
Net loss per share	$	(6.66	)	$	(5.98	)	$	(1.03	)	$	(0.43	)

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Apr. 30, 2018

Accounting Policies [Abstract]

Principles of Consolidation

Use of Estimates

Foreign Currency

Segment Reporting

Cash and Cash Equivalents

Research and Development Tax Credit Receivable

Property and Equipment

Asset Classification		Estimated Useful Life
Machinery and equipment		1-5 Years
Computer equipment		3-4 Years
Motor vehicles		4 Years
Leasehold improvements		5 Years or term of lease, if shorter

Revenue Recognition

Research and Development

Research and development: Research and development costs are expensed as incurred and include, but are not limited to:

•

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

•

Costs associated with preclinical and development activities;

•

Costs associated with regulatory operations.

Income Taxes

Stock Based Compensation

Net Loss per Share Attributable to Common Shareholders

Potential dilutive common share equivalents consist of:

	April 30,
	2018		2017		2016
Preferred stock		—		—		24,322,898
Stock options		388,366		148,469		76,643

Basic and diluted net loss per share	April 30,
	2018			2017			2016
Net loss	$	(15,805	)	$	(18,603	)	$	(11,436	)
Less: dividend on Series A		—			(935	)		(1,918	)
Less: dividend on Series B		—			(1,237	)		(2,121	)
Loss available to common stockholders		(15,805	)		(20,775	)		(15,475	)
Weighted average common shares, basic and diluted		10,321,780			4,646,764			591,298
Net loss per share, basic and diluted	$	(1.53	)	$	(4.47	)	$	(26.17	)

Fair Value Measurement

Correction

Recently Issued Accounting Pronouncements Adopted and Not Yet Adopted

Recently adopted accounting pronouncements

Consolidated Statements of Changes in Convertible Preferred Shares and Stockholders' Equity (Deficit) (Parenthetical) $ in Thousands	12 Months Ended
	Apr. 30, 2016 USD ($)
Series B Convertible Preferred Stock [Member]
Stock issuance costs	$ 186

Defined Contribution Plans	12 Months Ended
Defined Contribution Plans	Apr. 30, 2018
Compensation And Retirement Disclosure [Abstract]
Defined Contribution Plans	Note 10. Defined Contribution Plans Participation in a personal pension plan is available to all U.K. based employees of the Company upon commencement of their employment. Employer contributions are made in accordance with the terms and conditions of the employment contract. Employees may contribute in accordance with the prevailing statutory limitations. Employees of the U.S. parent company are eligible to participate in the Company's 401(k) Plan. The Company will match up to 4% of employee contributions to the Plan. Total employer contributions to both plans for the years ended April 30, 2018, 2017, and 2016 were $219,000, $90,000 and $70,000 respectively.

Other Income	12 Months Ended
Other Income	Apr. 30, 2018
Other Nonoperating Income Expense [Abstract]
Other Income	Note 11. Other Income As of April 30, 2018 and 2017, the Company had research and development tax credits totaling $6.8 million and $2.2 million, respectively. This tax credit is related to a tax scheme for small and medium enterprises in the United Kingdom as well as the R&D expenditure credit system. The Company is able to file a claim for cash credit in proportion to the Company’s R&D expenditure for the year. This amount was included in other income, as it is a refundable credit that does not depend on the Company’s ongoing tax status or position. The Company recognized $4.4 million, $2.3 million and $2.0 million related to these programs in the years ended April 30, 2018, 2017, and 2016, respectively.