Rapt Therapeutics revives IPO, files to raise $75M

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Flx Bio, now Rapt Therapeutics came to be when Bristol-Myers Squibb bought Flexus Biosciences and the Big Pharma offloaded the immuno-oncology assets it didn’t want into a new company. (Alexander Naumann/Pixabay)

Second time might be the charm for Rapt Therapeutics, which filed to raise up to $75 million in its IPO after postponing an earlier attempt in August. The move comes five months after the company renamed itself and just over three months after it filed its initial S-1 form with plans to reap up to $86 million in its Nasdaq debut. 

Rapt's plans for the cash haven’t changed—just the amount it’s aiming to raise. The company, known as Flx Bio until May, will use the proceeds to get FLX475, a CCR4 antagonist for the treatment of cancer, beyond proof of concept, as well as to get RPT193, a second CCR4 med, through phase 1 in atopic dermatitis. The cash will also bankroll the development of its early-stage inhibitor of general control nonderepressible 2, which plays a role in antitumor immunity and tumor cell survival, Rapt said in the filing. 

Rapt was born in 2015 when Bristol-Myers Squibb bought Flexus Biosciences. The Big Pharma offloaded the immuno-oncology assets it didn’t want into Flx Bio. The new company bagged $60 million in series C funding in December 2017 to advance FLX475, a drug designed block CCR4 to disrupt a pathway tumors use to recruit regulatory T cells—called Tregs—and tamp down their immune response to the tumor. 

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RELATED: Flx Bio keeps it capital in Rapt Therapeutics rebrand 

At the time, the company planned to select a second clinical candidate targeting the enzyme ubiquitin specific protease 7, which plays a role in two cancer pathways. But it went in a different direction. 

Unlike FLX475, which focuses on regulatory T cells, the inflammation candidate RPT193 takes aim at helper T cells. Tregs suppress other immune cells to shut down the immune response—for example, to prevent autoimmune disease—while helper T cells activate other immune cells. RPT193 is designed to block the movement of type 2 helper T cells into inflamed tissues and reduce inflammation in diseases such as asthma and rhinosinusitis as well as atopic dermatitis. 

The company renamed itself in May this year to reflect this expansion into allergy and inflammatory diseases.

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