Segment Reporting - Financial Information with Respect to Company's Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Reporting Information [Line Items]
Revenue	$ 5,389	$ 1,874	$ 10,851	$ 3,402
Total allocation of centralized research and development operational cash expenditures	22,760	10,869	42,721	18,986
Loss from operations	(23,871)	(12,125)	(43,365)	(21,360)
Adjustments to reconcile segment operating loss to consolidated loss from operations:
Interest income received	(1,485)	(299)	(2,086)	(522)
Depreciation and amortization			(2,107)	(970)
Share-based compensation			(3,828)	(405)
Loss on disposal of assets			(22)	(8)
Changes in prepaids, accounts payable and accrued expenses	6,884	(2,491)	10,809	2,906
Operating Segments
Segment Reporting Information [Line Items]
Revenue			10,851	3,402
Total segment operational cash expenditures	16,949	5,600	31,966	15,909
Total allocation of centralized research and development operational cash expenditures	3,118	2,721	6,871	5,175
Loss from operations	(14,678)	(6,447)	(27,986)	(17,682)
Operating Segments \| Therapeutics
Segment Reporting Information [Line Items]
Revenue	4,819	1,447	9,638	2,894
Total segment operational cash expenditures	14,872	4,926	27,782	14,176
Total allocation of centralized research and development operational cash expenditures	3,118	1,905	6,871	3,942
Loss from operations	(13,171)	(5,384)	(25,015)	(15,224)
Operating Segments \| Food
Segment Reporting Information [Line Items]
Revenue	570	427	1,213	508
Total segment operational cash expenditures	2,077	674	4,184	1,733
Total allocation of centralized research and development operational cash expenditures		816		1,233
Loss from operations	(1,507)	(1,063)	(2,971)	(2,458)
Segment Reconciling Items
Adjustments to reconcile segment operating loss to consolidated loss from operations:
Corporate general and administrative cash expenditures	(11,123)	(2,118)	(18,145)	(4,677)
Interest income received	(1,485)	(299)	(2,086)	(522)
Depreciation and amortization	(1,168)	(512)	(2,107)	(970)
Share-based compensation	(2,279)	(255)	(3,828)	(405)
Loss on disposal of assets	$ (22)	$ (3)	$ (22)	$ (10)

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The aggregate costs incurred (1) in a planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge will be useful in developing a new product or service, a new process or technique, or in bringing about a significant improvement to an existing product or process; or (2) to translate research findings or other knowledge into a plan or design for a new product or process or for a significant improvement to an existing product or process whether intended for sale or the entity's use, during the reporting period charged to research and development projects, including the costs of developing computer software up to the point in time of achieving technological feasibility, and costs allocated in accounting for a business combination to in-process projects deemed to have no alternative future use.

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