Nature of the Business - Additional Information (Detail)				1 Months Ended		3 Months Ended		12 Months Ended
	Jan. 23, 2023 USD ($)	Sep. 15, 2021 USD ($)	Mar. 14, 2021 Poster	Mar. 31, 2022 USD ($)	Jul. 12, 2019 USD ($)	Mar. 31, 2023 USD ($)	Mar. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2022 USD ($)	Apr. 03, 2017 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Number of posters on NRGI fusions | Poster			2
Accumulated deficit						$ 547,907,000			$ 547,636,000
Net loss from continuing operations						271,000	$ 132,000
Cash used in operating activities						356,000	$ 354,000
Cash, cash equivalents and marketable securities						$ 19,400,000
Asset Purchase Option Agreement [Member]
Summary Of Significant Accounting Policies [Line Items]
Transaction expenses	$ 11,000
Gain related to option fee payment	$ 139,000							$ 100,000
Terms of exercise option	The Purchaser may exercise the Option prior to July 23, 2023
Asset Purchase Option Agreement [Member] | Pegascy SAS [Member]
Summary Of Significant Accounting Policies [Line Items]
Consideration receivable	$ 700,000	$ 500,000
Option fee	$ 150,000	$ 100,000
Consideration received				$ 500,000
Gain related to payment of consideration				$ 500,000
Exercise period of option		24 months
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 Adenocarcinoma of Pancreas [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