Nature of the Business - Additional Information (Detail) - USD ($)		1 Months Ended		3 Months Ended		9 Months Ended
	Sep. 15, 2021	Mar. 27, 2020	Jul. 12, 2019	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Apr. 03, 2017
Summary Of Significant Accounting Policies [Line Items]
Accumulated deficit				$ 545,617,000		$ 545,617,000		$ 543,637,000
Net loss from continuing operations				525,000	$ 1,006,000	1,980,000	$ 1,920,000
Cash used in operating activities						137,000	$ (2,849,000)
Cash, cash equivalents and marketable securities				14,600,000		14,600,000
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
Asset Purchase Option Agreement [Member]
Summary Of Significant Accounting Policies [Line Items]
Gain related to option fee payment				$ 100,000		$ 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
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