Nature of the Business - Additional Information (Detail) - USD ($)	1 Months Ended		6 Months Ended
	Mar. 27, 2020	Jul. 12, 2019	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Apr. 03, 2017
Summary Of Significant Accounting Policies [Line Items]
Accumulated deficit			$ 545,092,000		$ 543,637,000
Net loss from continuing operations			1,500,000
Cash used in operating activities			582,000	$ (2,984,000)
Cash, cash equivalents and marketable securities			$ 14,900,000
Celator Pharmaceuticals Inc [Member]
Summary Of Significant Accounting Policies [Line Items]
Cash payment received	$ 2,300,000
Reimbursement of expenses	200,000
Transaction expenses	$ 400,000
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 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