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Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Jul. 31, 2018	Sep. 10, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jul. 31, 2018
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Trading Symbol	KALV
Entity Registrant Name	KALVISTA PHARMACEUTICALS, INC.
Entity Central Index Key	0001348911
Current Fiscal Year End Date	--04-30
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		17,179,687

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jul. 31, 2018	Apr. 30, 2018
Current assets:
Cash and cash equivalents	$ 48,070	$ 51,055
Research and development tax credit receivable	5,604	6,834
Prepaid expenses and other current assets	1,511	1,491
Total current assets	55,185	59,380
Other assets	173	173
Property and equipment, net	2,260	1,836
Total assets	57,618	61,389
Current liabilities:
Accounts payable	2,345	1,433
Accrued expenses	3,137	3,087
Deferred revenue - current portion	17,207	18,475
Capital lease liability - current portion	214	221
Total current liabilities	22,903	23,216
Long-term liabilities:
Deferred revenue - net of current portion	8,465	10,862
Capital lease liability - net of current portion		58
Total long-term liabilities	8,465	10,920
Commitments and contingencies (Note 4)
Stockholders’ equity
Common stock, $0.001 par value Shares authorized: 100,000,000 Shares issued and outstanding: 10,792,646	11	11
Additional paid-in capital	105,358	100,011
Accumulated deficit	(76,690)	(71,660)
Accumulated other comprehensive loss	(2,429)	(1,109)
Total stockholders’ equity	26,250	27,253
Total liabilities and stockholders’ equity	$ 57,618	$ 61,389

Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Jul. 31, 2018	Jul. 31, 2017
Income Statement [Abstract]
Revenue	$ 3,718	$ 96
Operating expenses:
Research and development	8,356	3,476
General and administrative	2,371	2,073
Total operating expenses	10,727	5,549
Operating loss	(7,009)	(5,453)
Other income:
Interest income	89	2
Foreign currency exchange gain (loss)	67	(32)
Other income	1,823	555
Total other income	1,979	525
Net loss	(5,030)	(4,928)
Other comprehensive loss:
Foreign currency translation adjustments	(1,320)	116
Comprehensive loss	$ (6,350)	$ (4,812)
Net loss per share to common stockholders, basic and diluted	$ (0.47)	$ (0.51)
Weighted average common shares outstanding, basic and diluted	10,799,895	9,713,042

Condensed Consolidated Statement of Changes in Stockholders' Equity (Unaudited) - 3 months ended Jul. 31, 2018 - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balance at Apr. 30, 2018	$ 27,253	$ 11	$ 100,011	$ (71,660)	$ (1,109)
Balance, shares at Apr. 30, 2018		10,799,895
Cash received pursuant to common stock subscription agreement	5,000		5,000
Stock-based compensation expense	347		347
Net loss	(5,030)			(5,030)
Foreign currency translation	(1,320)				(1,320)
Balance at Jul. 31, 2018	$ 26,250	$ 11	$ 105,358	$ (76,690)	$ (2,429)
Balance, shares at Jul. 31, 2018		10,799,895

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Jul. 31, 2018	Jul. 31, 2017
Cash Flows from Operating Activities
Net loss	$ (5,030)	$ (4,928)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	50	32
Stock-based compensation expense	347	221
Foreign currency remeasurement loss	6	32
Changes in operating assets and liabilities:
Research and development tax credit receivable	919	(530)
Prepaid expenses and other current assets	(69)	(85)
Grants and other receivables		224
Accounts payable	1,126	771
Accrued expenses	157	(185)
Deferred revenue	(3,718)
Net cash used in operating activities	(6,212)	(4,448)
Cash Flows from Investing Activities
Acquisition of property and equipment	(565)	(110)
Net cash used in investing activities	(565)	(110)
Cash Flows from Financing Activities
Capital lease principal payments	(52)
Issuance of common stock	5,000
Net cash from financing activities	4,948
Effect of exchange rate changes on cash and cash equivalents	(1,156)	64
Net decrease in cash and cash equivalents	(2,985)	(4,494)
Cash and cash equivalents at beginning of period	51,055	30,950
Cash and cash equivalents at end of period	48,070	26,456
Supplemental Disclosures of Non-cash Financing Activities
Capital leases		$ 513
Acquisition of property and equipment in accounts payable	$ 100

The Company

3 Months Ended

Jul. 31, 2018

Organization Consolidation And Presentation Of Financial Statements [Abstract]

The Company

1.	The Company

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 what it believes will be best-in-class oral therapies. In December 2017, the Company initiated a first-in-human study of KVD900. 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. The Company is currently planning to initiate a Phase 2 clinical trial that it expects to initiate in late 2018 and complete in mid-2019. The Company anticipates that this trial will be designed as a proof of concept study in HAE patients, intended to determine the safety and efficacy of KVD900 in reducing the severity and duration of attacks when taken at the onset of symptoms. 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 be completed in the second half of 2019.

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 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 and sale of preferred stock, common stock, the share purchase transaction with Carbylan, the Option Agreement and grant income. As of July 31, 2018, the Company had an accumulated deficit of $76.7 million and $48.1 million of cash and cash equivalents. The Company’s working capital, primarily cash, along with the additional proceeds from the sale of common stock discussed in Note 6, is anticipated to fund the Company’s operations for at least the next twelve months from the date these interim condensed consolidated financial statements are issued. Accordingly, the unaudited interim condensed 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 it becomes 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

3 Months Ended

Jul. 31, 2018

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2.	Summary of Significant Accounting Policies

Principles of Consolidation: The accompanying unaudited interim condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiary. All intercompany transactions and balances have been eliminated in consolidation.

The accompanying unaudited interim condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) for interim financial information and in accordance with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements. Such financial statements reflect all adjustments that are, in management’s opinion, necessary to present fairly, in all material respects, the Company’s consolidated financial position, results of operations, and cash flows. There were no adjustments other than normal recurring adjustments. The unaudited interim condensed consolidated financial statements have been prepared on the same basis as the annual financial statements. These unaudited interim condensed consolidated financial results are not necessarily indicative of the results to be expected for the year ending April 30, 2019, or for any other future annual or interim period. The accompanying unaudited interim condensed consolidated financial statements should be read in conjunction with the audited financial statements as of and for the year ended April 30, 2018.

Segment Reporting: The Company’s 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.

Net Loss per Share: Basic net loss per share is computed by dividing the net loss by the weighted average number of common shares outstanding during the period. Diluted net loss per share is computed by dividing net loss by the sum of the weighted average number of common shares and the number of dilutive potential common share equivalents outstanding during the period. Potential dilutive common share equivalents consist of the incremental common shares issuable upon the exercise of vested share options.

Potential dilutive common share equivalents consist of:

	July 31,
	2018		2017
Stock Options		1,239,861		183,169

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

Revenue Recognition: We recognize revenue from research and development arrangements and grant income. In accordance with Accounting Standards Codification (“ASC”) 606, revenue is recognized when a customer obtains control of promised goods or services. The amount of revenue recognized reflects the consideration to which the Company expects to be entitled to receive in exchange for these goods and services.

Performance obligations promised in a contract are identified based on the goods and services that will be transferred to the customer that are both capable of being distinct, whereby the customer can benefit from the good or service either on its own or together with other available resources, and are distinct in the context of the contract, whereby the transfer of the good or service is separately identifiable from other promises in the contract. To the extent a contract includes multiple promised goods and services, the Company must apply judgment to determine whether promised goods and services are capable of being distinct and distinct in the context of the contract. If these criteria are not met, the promised goods and services are accounted for as a combined performance obligation.

The transaction price is determined based on the consideration to which the Company will be entitled in exchange for transferring goods and services to the customer. To the extent the transaction price includes variable consideration, the Company estimates the amount of variable consideration that should be included in the transaction price utilizing either the expected value method or the most likely amount method depending on the nature of the variable consideration. Variable consideration is included in the transaction price if, in the Company’s judgment, it is probable that a significant future reversal of cumulative revenue under the contract will not occur. Any estimates, including the effect of the constraint on variable consideration, are evaluated at each reporting period for any changes.

If the contract contains a single performance obligation, the entire transaction price is allocated to the single performance obligation. Contracts that contain multiple performance obligations require an allocation of the transaction price to each performance obligation on a relative standalone selling price basis unless the transaction price is variable and meets the criteria to be allocated entirely to a performance obligation or to a distinct service that forms part of a single performance obligation. The consideration to be received is allocated among the separate performance obligations based on relative standalone selling prices.

The Company satisfies performance obligations either over time or at a point in time. Revenue is recognized over time if either 1) the customer simultaneously receives and consumes the benefits provided by the entity’s performance, 2) the entity’s performance creates or enhances an asset that the customer controls as the asset is created or enhanced, or 3) the entity’s performance does not create an asset with an alternative use to the entity and the entity has an enforceable right to payment for performance completed to date. If the entity does not satisfy a performance obligation over time, the related performance obligation is satisfied at a point in time by transferring the control of a promised good or service to a customer. Examples of control are using the asset to produce goods or services, enhance the value of other assets, settle liabilities, and holding or selling the asset. ASC 606 requires the Company to select a single revenue recognition method for the performance obligation that faithfully depicts the Company’s performance in transferring control of the goods and services. The guidance allows for two methods to measure progress toward complete satisfaction of a performance obligation, depending on the facts and circumstances:

Output methods - recognize revenue on the basis of direct measurements of the value to the customer of the goods or services transferred to date relative to the remaining goods or services promised under the contract (e.g., surveys of performance completed to date, appraisals of results achieved, milestones reached, time elapsed, and units of produced or units delivered); and

Input methods - recognize revenue on the basis of the entity’s efforts or inputs to the satisfaction of a performance obligation (e.g., resources consumed, labor hours expended, costs incurred, or time elapsed) relative to the total expected inputs to the satisfaction of that performance obligation.

Licenses of intellectual property: If the license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company must consider the nature of the intellectual property to which the customer will have rights (i.e., access at a point in time or benefit of intellectual property enhancements over time). The Company recognizes revenue from non-refundable, up-front fees allocated to the license at a point in time/over the period the license is transferred to the customer and the customer is able to use and benefit from the license. For licenses that are bundled with other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue from non-refundable, up-front fees. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition.

Milestone payments: At the inception of each arrangement that includes development and regulatory milestone payments for promised goods and services, the Company evaluates the circumstances of whether the milestones will be reached and estimates the amount to be included in the transaction price that will not cause a significant revenue reversal. The Company will evaluate these types of payments for customer options once those options have been exercised. ASC 606 suggests two alternatives to use when estimating the amount of variable consideration: the expected value method and the most likely amount method. Under the expected value method, an entity considers the sum of probability-weighted amounts in a range of possible consideration amounts. Under the most likely amount method, an entity considers the single most likely amount in a range of possible consideration amounts. The Company will use the most likely amount method for development and regulatory milestone payments. Management believes the most likely amount method is the better predictor as the Company expects to be entitled to only one of two possible amounts. Additionally, management believes that the most likely amount of milestone consideration is its stated amount. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price. The transaction price is then allocated to performance obligations on a specific basis or on a relative stand-alone selling price basis. The Company recognizes revenue as or when the performance obligations under the contract are satisfied. At the end of each subsequent reporting period, the Company re-evaluates whether it is probable that a significant revenue reversal will not occur in future periods, and if necessary, adjusts its estimates of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect revenues and earnings in the period of adjustment.

Royalties: For arrangements that include sales-based royalties, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied).

Up-front payments: Up-front payments and fees are recorded as deferred revenue upon receipt or when due and may require deferral of revenue recognition to a future period until the Company performs its obligations under these arrangements. Amounts payable to the Company are recorded as accounts receivable when the Company’s right to consideration is unconditional. The Company does not assess whether a contract has a significant financing component if the expectation at contract inception is such that the period between payment by the customer and the transfer of the promised goods or services to the customer will be one year or less.

Contract Balances: The Company recognizes a contract asset when the Company transfers goods or services to a customer before the customer pays consideration or before payment is due, excluding any amounts presented as a receivable (i.e., accounts receivable). A contract asset is an entity’s right to consideration in exchange for goods or services that the entity has transferred to a customer. The contract liabilities (i.e. deferred revenue) primarily relate to contracts where we have received payment but we have not yet satisfied the related performance obligations. The advance consideration received from customers for R&D services and/or licenses is a contract liability, recorded as deferred revenue, until the underlying performance obligations are transferred to the customer.

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.

Recently Issued Accounting Pronouncements Not Yet Adopted: 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 fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. Early application is permitted, however, the Company does not intend to early adopt. See Note 4 for additional information regarding the Company’s lease obligations.

Recently Adopted Accounting Pronouncements: 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 replaced most existing revenue recognition guidance in U.S. GAAP when it became effective and permits the use of either the retrospective or cumulative effect transition method. The Company adopted the updated standard May 1, 2018 using the modified retrospective method of adoption for all open contracts. The Company’s only significant revenue generating arrangement is the arrangement with Merck and is discussed in Note 5. The adoption of this guidance on the consolidated financial statements had no impact on the date of adoption and through July 31, 2018, other than the enhanced footnote disclosures.

Commitments and Contingencies

3 Months Ended

Jul. 31, 2018

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

4.	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 contractual obligations related to the expected future costs to be incurred to complete the ongoing toxicology studies and clinical trials. The remaining commitments, which have cancellation provisions, total $7.8 million at July 31, 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 $170,000 and $130,000 for the three months ended July 31, 2018 and 2017. Rent expense is reflected in general and administrative expenses and research and development expenses as determined by the underlying activities.

Future minimum lease payments under these leases as of July 31, 2018 are as follows (in thousands):

Fiscal Year	Capital Leases			Operating Leases
2019	$	163		$	272
2020		55			324
2021					327
2022		—			330
2023 and thereafter		—			715
Total minimum lease payments		218		$	1,968
Less amounts representing interest		(4	)
Present value of minimum payments		214

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 such expenditures can be reasonably estimated. There are no contingent liabilities requiring accrual at July 31, 2018.

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 $1.0 million within 90 days of the first commercial sale of the product subject to certain limitations, 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.

Merck Arrangement	3 Months Ended
Merck Arrangement	Jul. 31, 2018
License And Collaboration Arrangements [Abstract]
Merck Arrangement	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 $37.0 million to KalVista Limited in November 2017. If Merck exercises both options under the Option Agreement, KalVista Limited could receive up to an additional $715.0 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, are for a single commercial objective and therefore should be combined as one arrangement for accounting purposes. The aggregate proceeds from the arrangement were allocated to the equity arrangement and to the revenue arrangement. The Company evaluated the revenue arrangement in accordance with the provisions of ASC 606 upon the adoption of this guidance on May 1, 2018. The Company determined that the revenue arrangement contains the following promised services: (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, and (iii) research and development services related to the development of the Oral DME Compounds. The Company has determined that Merck’s options to acquire KVD001 and the Oral DME Compounds are customer 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 below their standalone selling prices and do not grant the customer a material right. Consequently, the Company determined that Merck’s options are not performance obligations at the inception of the arrangement. The Company further determined that the research license granted is not distinct 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 and is significantly interdependent with the respective research and development services. 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 performance obligations (the “KVD001 Performance Obligation” and the “Oral DME Performance Obligation”). Therefore, the Company has identified two performance obligations under the revenue arrangement as follows: (i) the KVD001 Performance Obligation, and (ii) the Oral DME Performance Obligation. The transaction price that is allocable at inception of the arrangement is comprised of the non-refundable upfront 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 was recorded in stockholders’ equity at the date of issuance. The Company allocated the remaining transaction price of $37.0 million to the remaining performance obligations using the relative standalone selling price. There is uncertainty that the events to obtain and the development and regulatory milestones will be achieved given the nature of clinical development and the stage of the research. The development and regulatory milestones will be constrained until the Company is sure that a significant revenue reversal will not occur. The royalties and sales-based milestones relate predominantly to a license of intellectual property and are determined by sales or usage-based thresholds. The royalties and sales-based milestones will be accounted for under the royalty recognition constraint and will not recognize revenue for each until the subsequent sale of a licensed product (achievement of each) occurs. The Company developed the Stand-alone Selling Price (“SSP”) for the KVD001 Performance Obligation and Oral DME Performance by applying an analysis of discounted cash flows and the transaction price was allocated among the separate performance obligations using the relative standalone selling price method. The amount allocated to each Performance Obligation will be recognized as revenue using an input method of performance completed to date comparing the total effort incurred with the Company’s estimate of total effort required to perform the R&D services for each respective performance obligation. For the three months ended July 31, 2018, the Company recognized approximately $3.7 million of revenue with respect to the arrangement with Merck, all of which was recognized from the deferred revenue balance. For the three months ended July 31, 2018, deferred revenue on the consolidated balance sheet is $25.7 million, which is related to the remaining unsatisfied performance obligations in this arrangement. Approximately $17.2 million related to the unsatisfied performance obligation is expected to be satisfied in the next 12 months and the remaining $8.5 million will be satisfied in the 4 years thereafter. Upon adoption of ASC 606 on May 1, 2018, the Company concluded that there was no change in the amount or timing of revenue recognition as compared to its historical practices for this arrangement. Accordingly, there was no adjustment upon adoption.

Summary of Significant Accounting Policies (Policies)

3 Months Ended

Jul. 31, 2018

Accounting Policies [Abstract]

Principles of Consolidation

Segment Reporting

Net Loss per Share

Potential dilutive common share equivalents consist of:

	July 31,
	2018		2017
Stock Options		1,239,861		183,169

Revenue Recognition

Fair Value Measurement

Recently Issued Accounting Pronouncements Adopted and Not Yet Adopted

Commitments and Contingencies - Schedule of Future Minimum Lease Payments Under Capital and Operating Leases (Detail) $ in Thousands	Jul. 31, 2018 USD ($)
Capital Leases
2019	$ 163
2020	55
Total minimum lease payments	218
Less amounts representing interest	(4)
Present value of minimum payments	214
Operating Leases
2019	272
2020	324
2021	327
2022	330
2023 and thereafter	715
Total minimum lease payments	$ 1,968

Merck Arrangement - Additional Information (Detail)		1 Months Ended	3 Months Ended
Merck Arrangement - Additional Information (Detail)	Oct. 06, 2017 USD ($) PerformanceObligation $ / shares shares	Nov. 30, 2017 USD ($)	Jul. 31, 2018 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Proceeds from issuance of common stock			$ 5,000,000
Number of performance obligations \| PerformanceObligation	2
Research and Development Services for KVD001 and Oral DME [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of performance obligations \| PerformanceObligation	2
Option Agreement [Member] \| Research and Development Services for KVD001 and Oral DME [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Transaction price allocable for non refundable upfront payment in performance obligations	$ 37,000,000
Merck Sharp & Dohme Corp. [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognized			3,700,000
Merck Sharp & Dohme Corp. [Member] \| Remaining Unsatisfied Performance Obligations [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue			$ 25,700,000
Merck Sharp & Dohme Corp. [Member] \| Stock Purchase Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Proceeds from issuance of common stock	$ 9,100,000
Number of shares of common stock issued \| shares	1,070,589
Price per share of common stock issued \| $ / shares	$ 8.50
Transaction price allocable for payment to common stock of performance obligations	$ 9,100,000
KalVista Pharmaceuticals Limited [Member] \| Merck Sharp & Dohme Corp. [Member] \| Option Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Agreement commencement date			Oct. 06, 2017
Non-refundable upfront fee		$ 37,000,000
Maximum additional option exercise payments and clinical, regulatory, and sales-based milestone payments could be received if options exercised	$ 715,000,000

Financing	3 Months Ended
Financing	Jul. 31, 2018
Equity Financing [Abstract]
Financing	6. Financing On July 30, 2018 the Company entered into Subscription Agreements with a group of investors to sell a total of 1,778,320 new shares of the Company’s common stock at a price of $8.21 per share. The total proceeds to the Company were $14.6 million, of which $5.0 million was received on July 31, 2018 and is included in cash and cash equivalents on the condensed consolidated balance sheet. The remaining $9.6 million was received on August 2, 2018.

Subsequent Events	3 Months Ended
Subsequent Events	Jul. 31, 2018
Subsequent Events [Abstract]
Subsequent Events	7. Subsequent Events On September 10, the Company issued 4,600,000 new shares of common stock at a price of $17.00 in a public offering, including the underwriters’ full exercise of the over-allotment option. The total net proceeds to the Company were $73.3 million, after deducting underwriting discounts, commissions and estimated offering expenses payable by the Company. Certain of the Company’s stockholders affiliated with its directors purchased an aggregate of 1,117,648 shares of common stock in this offering at the public offering price.

Accrued Expenses - Schedule of Accrued Expenses (Detail) - USD ($) $ in Thousands	Jul. 31, 2018	Apr. 30, 2018
Payables And Accruals [Abstract]
Accrued compensation expense	$ 544	$ 1,192
Accrued research expense	2,141	1,393
Accrued professional fees	291	164
Other accrued expenses	161	338
Total accrued expenses	$ 3,137	$ 3,087

Commitments and Contingencies - Additional Information (Detail) - USD ($)	3 Months Ended
	Jul. 31, 2018	Jul. 31, 2017
Other Commitments [Line Items]
Contractual obligations remaining commitments including cancellation provisions	$ 7,800,000
Maximum [Member]
Other Commitments [Line Items]
Royalty payable upon completion of first commercial sale	$ 1,000,000
Royalty payment obligations expiration period	90 days
Indemnification Guarantee [Member]
Other Commitments [Line Items]
Contingent liabilities	$ 0
General and Administrative Expenses and Research and Development Expenses [Member]
Other Commitments [Line Items]
Rent expense	$ 170,000	$ 130,000

Merck Arrangement - Additional Information (Detail 1) - Merck Sharp & Dohme Corp. [Member] $ in Millions	Jul. 31, 2018 USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2018-08-01
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue, remaining performance obligation	$ 17.2
Revenue, remaining performance obligation, expected timing of satisfaction, period	12 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2019-08-01
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue, remaining performance obligation	$ 8.5
Revenue, remaining performance obligation, expected timing of satisfaction, period	4 years

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Jul. 31, 2018	Apr. 30, 2018
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	10,799,895
Common stock, shares outstanding	10,799,895	10,799,895

The Company - Additional Information (Detail) - USD ($) $ in Thousands	Jul. 31, 2018	Apr. 30, 2018	Jul. 31, 2017	Apr. 30, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Accumulated deficit	$ 76,690	$ 71,660
Cash and cash equivalents	$ 48,070	$ 51,055	$ 26,456	$ 30,950

Summary of Significant Accounting Policies - Schedule of Potential Dilutive Common Share Equivalents (Detail) - shares	3 Months Ended
	Jul. 31, 2018	Jul. 31, 2017
Stock Options [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Number of anti-dilutive potential common share equivalents outstanding	1,239,861	183,169

Financing - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended	3 Months Ended
	Aug. 02, 2018	Jul. 30, 2018	Jul. 31, 2018
Securities Financing Transaction [Line Items]
Issuance of common stock			$ 5,000
Subscription Agreements [Member]
Securities Financing Transaction [Line Items]
Number of shares of common stock issued		1,778,320
Price per common stock		$ 8.21
Issuance of common stock		$ 14,600	$ 5,000
Subscription Agreements [Member] \| Subsequent Event [Member]
Securities Financing Transaction [Line Items]
Issuance of common stock	$ 9,600

Subsequent Events - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended
	Sep. 10, 2018	Jul. 31, 2018
Subsequent Event [Line Items]
Issuance of common stock		$ 5,000
Public Offering [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Number of shares of common stock issued	4,600,000
Price per common stock	$ 17.00
Issuance of common stock	$ 73,300
Public Offering [Member] \| Subsequent Event [Member] \| Stockholders Affiliated with Directors [Member]
Subsequent Event [Line Items]
Number of shares of common stock issued	1,117,648