CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) - USD ($) $ in Thousands	Jun. 30, 2026	Mar. 31, 2026	Dec. 31, 2025
Current assets:
Cash and cash equivalents	$ 2,366		$ 4,256
Restricted cash and cash equivalents			4,502
Investments	6,221		4,356
Grant receivable	1,761		322
Other current assets	1,423		1,734
Total current assets	11,771		15,170
Property and equipment, net	1,409		257
Operating lease right-of-use assets	43		70
Goodwill	372		372
Intangible assets, net	265		333
Other assets	170		123
Total assets	14,030		16,325
Current liabilities:
Accounts payable and accrued expenses	7,550		5,920
Investor liability pursuant to Letter Agreement			4,502
Operating lease liability	44		56
Deferred grant liability	927		927
Line of credit	0		750
Other liabilities	46		159
Total current liabilities	8,567		12,314
Noncurrent operating lease liability			15
Total liabilities	8,567		12,329
Commitments and contingencies (Note 8)
Stockholders' equity:
Preferred stock, $0.001 par value; 5,000,000 shares authorized; 1,952 shares issued and outstanding as of June 30, 2026 and December 31, 2025, respectively
Common stock, $0.001 par value; 2,000,000,000 shares authorized; 7,320,345 and 5,557,371 shares issued as of June 30, 2026 and December 31, 2025, respectively; 7,310,008 and 5,547,034 shares outstanding as of June 30, 2026 and December 31, 2025, respectively	7		6
Treasury stock (at cost), 10,337 shares as of June 30, 2026 and December 31, 2025, respectively	(500)		(500)
Additional paid-in capital	537,773		520,355
Accumulated deficit	(531,817)		(515,865)
Total stockholders' equity	5,463	$ 11,961	3,996
Total liabilities and stockholders' equity	$ 14,030		$ 16,325

Investor liability pursuant to letter agreement.

No definition available.

Name:	pstv_InvestorLiabilityPursuantToLetterAgreement
Namespace Prefix:	pstv_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Sum of the carrying values as of the balance sheet date of obligations incurred through that date and due within one year (or the operating cycle, if longer), including liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received, taxes, interest, rent and utilities, accrued salaries and bonuses, payroll taxes and fringe benefits.