Spruce Biosciences' stock leaped over 90% in early premarket trading on Tuesday, topping the Stocktwits trending list, hours after investor Martin Shkreli disclosed his long position on the stock and discussed his optimistic outlook.

That's after SPRB stock gained a staggering 1,378% to $130.4 in Monday's session, following the company's announcement that it received the FDA's 'Breakthrough Therapy Designation' for its new therapy for a rare neurological disease.

Spruce's tralesinidase alfa enzyme replacement therapy (TA-ERT) is designed to treat Sanfilippo syndrome type B (MPS IIIB), a rare, inherited lysosomal storage disease that causes a gradual decline in motor skills and cognition, as well as hyperactivity with aggressive behavior.

Shkreli said in an X post early Tuesday he believes the said treatment "will be approved" and become "the new standard of care," forecasting that it would push Spruce's stock to $500. Shkreli, a former hedge fund manager and pharmaceutical executive who has served time in jail for securities fraud, did not provide a timeline.

"I was working on a presentation when the news was scooped. but this drug restores the abnormally high levels of heparan sulfate to normal. without this drug, patients will die at 18. with normal ranges of HS, they may live a normal life," he said in a follow-up post.

CEO Javier Szwarcberg said on Monday that the company is preparing to submit an application for approval of the therapy in MPS IIIB in the first quarter of 2026. According to Spruce, Sanfilippo Syndrome Type B affects one in 200,000 people in the U.S.

FDA's 'Breakthrough Therapy Designation' expedites the development and regulatory review of promising therapies for serious or life-threatening conditions, with intensive FDA guidance.

Notably, Shkreli also recently revealed a short position in Opendoor Technologies' shares, a widely watched meme stock.

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