Nature of the Business - Additional Information (Detail) - USD ($)			1 Months Ended	3 Months Ended
	Feb. 13, 2024	Jan. 23, 2023	Jul. 12, 2019	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023	Apr. 03, 2017
Summary Of Significant Accounting Policies [Line Items]
Accumulated deficit				$ 347,447,000		$ 548,817,000
Net loss from continuing operations				(436,000)	$ (271,000)
Cash used in operating activities				1,314,000	$ 356,000
Cash and cash equivalents and short-term investments				$ 244,100,000
Asset Purchase Option Agreement [Member]
Summary Of Significant Accounting Policies [Line Items]
Gain related to option fee payment		$ 100,000
Terms of exercise option		The Purchaser decided not to exercise the Option in July 2023
Asset Purchase Option Agreement [Member] | Pegascy SAS [Member]
Summary Of Significant Accounting Policies [Line Items]
Consideration receivable		$ 700,000
Option fee		200,000
Asset Purchase Option Agreement [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Transaction expenses		$ 100,000
Ipsen [Member]
Summary Of Significant Accounting Policies [Line Items]
Additional contingent milestone payments	$ 225,000,000
Ipsen [Member] | Asset Sale Agreement [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Contingent milestone payments receivable							$ 225,000,000.0
Ipsen [Member] | First Line Treatment of Metastatic Adenocarcinoma of Pancreas [Member]
Summary Of Significant Accounting Policies [Line Items]
Contingent milestone payments received	225,000,000
Ipsen [Member] | First Line Treatment Of Metastatic Pancreatic Ductal Adenocarcinoma [Member]
Summary Of Significant Accounting Policies [Line Items]
Contingent milestone payments received	$ 225,000,000
Ipsen [Member] | After Failure of First Line Chemotherapy [Member]
Summary Of Significant Accounting Policies [Line Items]
Contingent milestone payments receivable							150,000,000
Ipsen [Member] | Additional Indication [Member]
Summary Of Significant Accounting Policies [Line Items]
Contingent milestone payments receivable							$ 75,000,000
14ner Sale [Member]
Summary Of Significant Accounting Policies [Line Items]
Upfront cash payment received			$ 3,500,000
14ner Sale [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Additional payments receivable on achievement of certain milestone events			54,500,000
14ner Sale [Member] | Achievement of the Primary Endpoint in the First Registrational Clinical Study of Either MM-121 or MM-111 [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Additional payments receivable on achievement of certain milestone events			3,000,000.0
14ner Sale [Member] | Achievement of Various Regulatory Approval and Reimbursement-Based Milestones in the United States, Europe and Japan [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Additional payments receivable on achievement of certain milestone events			16,500,000
14ner Sale [Member] | Achievement Various Cumulative Worldwide Net Sales Targets Between $100.0 million and $300.0 million for MM-121 and MM-111 [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Additional payments receivable on achievement of certain milestone events			35,000,000.0
Cumulative worldwide net sales target			$ 300,000,000.0