Development

Basking's BB-025 rapidly reverses stroke thrombolytic in Phase I study

Phase I data from the Study of BB-025, Alone and After BB-031, in Healthy Volunteers show that BB-025, the oligonucleotide reversal agent for Research...

Edited by Robert McTiernan··2 min read
Basking's BB-025 rapidly reverses stroke thrombolytic in Phase I study

Phase I data show that BB-025, the oligonucleotide reversal agent for North Carolina-based Basking Biosciences' investigational stroke thrombolytic BB-031, produced complete reversal of BB-031 activity within five minutes, with no serious adverse events and no treatment discontinuations, according to a press release. The result addresses a key uncertainty in Basking's paired-drug strategy: that a clinician-controlled antidote for BB-031 could work reliably and rapidly enough to be useful in acute stroke care.

BB-031 is an RNA aptamer that selectively inhibits von Willebrand factor (vWF), a central mediator of platelet-rich thrombus formation under high arterial shear. By disrupting vWF rather than activating the plasminogen cascade — the mechanism underlying both of the currently approved thrombolytics, Activase (alteplase) and TNKase (tenecteplase) — BB-031 is designed to promote thrombus dissolution without triggering systemic fibrinolysis. BB-025 is a complementary oligonucleotide that specifically binds BB-031, neutralizing its activity on demand.

In the first-in-human study, 60 adults received a single intravenous bolus of BB-025 at doses up to 12 mg/kg, either alone or following a single dose of BB-031 at doses up to 6 mg/kg. When administered after BB-031, BB-025 restored vWF activity and platelet function within five minutes. The reversal held at both 30-minute and five-hour post-BB-031 timepoints, supporting a durable effect across a clinically relevant window. No deaths, life-threatening treatment-emergent adverse events (TEAEs), or serious adverse events occurred, and no TEAE led to discontinuation. Bleeding events and infusion-related reactions were non-severe and transient. BB-031 itself was also generally well tolerated at doses up to 6 mg/kg.

Neither alteplase nor tenecteplase has an approved reversal agent. When patients develop symptomatic intracranial hemorrhage following thrombolysis — the most feared complication — clinicians have no direct pharmacological antidote. Basking's company asserts that BB-025 would be the first clinically validated reversal agent for any thrombolytic in the acute ischemic stroke (AIS) setting, though that claim remains contingent on regulatory approval of both agents.

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The BB-025 Phase I data arrive as BB-031 advances through the RAISE trial, a multicenter, randomized, double-blind, placebo-controlled Phase II study enrolling patients with AIS who present within 24 hours of symptom onset — a window five to eight times wider than the three-to-four-and-a-half-hour label for approved fibrinolytics. Part A of RAISE was completed in 2025, and Part B, expanded to approximately 180 patients, is currently recruiting at sites across North America and Australia. Preclinical work published in July 2026 showed BB-031 restored blood flow more effectively than both alteplase and tenecteplase in a microfluidic model using blood from AIS patients, including in clots matured for three to six hours.

Basking said it intends to incorporate BB-025 into the BB-031 AIS development program pending FDA discussions. The Phase I study was first initiated in November 2025, conducted in Australia. Detailed results will be presented at a future medical meeting.

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