Nature of the Business and Summary of Significant Accounting Policies - Additional Information (Detail)			1 Months Ended		12 Months Ended
	Jan. 23, 2023 USD ($)	Sep. 15, 2021 USD ($)	Mar. 31, 2022 USD ($)	Jul. 12, 2019 USD ($)	Dec. 31, 2022 USD ($) Segment Region	Dec. 31, 2021 USD ($)	Apr. 03, 2017 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Accumulated deficit					$ 547,636,000	$ 546,092,000
Net loss from continuing operations					1,544,000	2,455,000
Cash used in operating activities					1,742,000	218,000
Cash, cash equivalents and marketable securities					$ 19,400,000
Number of operating segments | Segment					1
Number of geographic regions | Region					1
Original maturities					Three months or less
Asset Purchase Option Agreement [Member]
Summary Of Significant Accounting Policies [Line Items]
Gain related to option fee payment						$ 100,000
Asset Purchase Option Agreement [Member] | Pegascy SAS [Member]
Summary Of Significant Accounting Policies [Line Items]
Consideration receivable		$ 500,000
Option fee		$ 100,000
Exercise period of option		24 months
Consideration received			$ 500,000
Gain related to payment of consideration			$ 500,000
Asset Purchase Option Agreement [Member] | Pegascy SAS [Member] | Subsequent Event [Member]
Summary Of Significant Accounting Policies [Line Items]
Consideration receivable	$ 700,000
Option fee	$ 200,000
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
Ipsen [Member] | Asset Sale Agreement [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Contingent milestone payments receivable							$ 450,000,000.0
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] | Maximum [Member] | Achievement of the Primary Endpoint in the First Registrational Clinical Study of Either MM-121 or MM-111 [Member]
Summary Of Significant Accounting Policies [Line Items]
Additional payments receivable on achievement of certain milestone events				3,000,000.0
14ner Sale [Member] | Maximum [Member] | Achievement of Various Regulatory Approval and Reimbursement-Based Milestones in the United States, Europe and Japan [Member]
Summary Of Significant Accounting Policies [Line Items]
Additional payments receivable on achievement of certain milestone events				16,500,000
14ner Sale [Member] | Maximum [Member] | Achievement Various Cumulative Worldwide Net Sales Targets Between $100.0 million and $300.0 million for MM-121 and MM-111 [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