Nature of the Business - Additional Information (Detail) - USD ($)			1 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended
	Jan. 23, 2023	Sep. 15, 2021	Mar. 31, 2022	Jul. 12, 2019	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2021	Dec. 31, 2022	Apr. 03, 2017
Summary Of Significant Accounting Policies [Line Items]
Accumulated deficit					$ 548,577,000		$ 548,577,000			$ 547,636,000
Net loss from continuing operations					279,000	$ 442,000	941,000	$ 1,052,000
Cash used in operating activities							1,227,000	$ 1,557,000
Cash and cash equivalents and short-term investment					$ 18,900,000		$ 18,900,000
Asset Purchase Option Agreement [Member]
Summary Of Significant Accounting Policies [Line Items]
Gain related to option fee payment	$ 100,000								$ 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	$ 500,000
Option fee	200,000	$ 100,000
Consideration received			$ 500,000
Net gain related to payment of consideration			$ 400,000
Exercise period of option		24 months
Asset Purchase Option Agreement [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Transaction expenses	$ 100,000
Ipsen [Member] | Asset Sale Agreement [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Contingent milestone payments receivable											$ 450,000,000.0
Ipsen [Member] | First Line Treatment of Metastatic Pancreatic Ductal Adenocarcinoma [Member]
Summary Of Significant Accounting Policies [Line Items]
Contingent milestone payments receivable											225,000,000.0
Ipsen [Member] | After Failure of First Line Chemotherapy [Member]
Summary Of Significant Accounting Policies [Line Items]
Contingent milestone payments receivable											150,000,000.0
Ipsen [Member] | Additional Indication [Member]
Summary Of Significant Accounting Policies [Line Items]
Contingent milestone payments receivable											$ 75,000,000.0
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