PhaseBio raised $34 million in its series D round, which will advance its lead assets: a treatment for pulmonary arterial hypertension (PAH) developed in-house and a reversal agent of AstraZeneca’s clot-busting Brilinta, licensed from the British pharma in 2017.

Its lead asset, PB1046, is based on its elastin-like polypeptide (ELP) technology, which it licensed from Duke University.

"It is, in essence, a half-life protraction technology platform," said PhaseBio CEO Jonathan Mow. What differentiates it from similar technologies is that it both increases the half-life of a drug and creates a depot under the skin where the drug is injected. As the drug is warmed in this area to body temperature, it is slowly released into circulation, where it will have a longer half-life, Mow said.

PhaseBio is using its platform to look at proteins, peptides and other large molecules that have suboptimal or frequent dosing based on their half-life. The goal is to extend the half-life and arrive at injectables that can be administered once a week, or even less frequently, Mow said.

"PB1046 is a result of that—it’s an analog of vasoactive intestinal peptide (VIP). Native VIP has a half-life of less than a minute. When we deliver it via subcutaneous injection, it has a half-life of 60 hours, which is amenable to once-weekly injection," he said. PhaseBio plans to push the candidate into phase 2 at the end of the year with a readout slated for late 2019 or early 2020.

The asset licensed from AstraZeneca, PB2542, is an antibody fragment that counters the effects of Brilinta by binding the drug and its active metabolite. It would be used for patients taking Brilinta who are either experiencing major bleeding or need to have urgent surgery—situations in which Brilinta’s anticlotting effects would need to be swiftly reversed. PhaseBio is looking to wrap up a phase 1 trial of PB2542 this year.

The series D includes the conversion of existing convertible promissory notes and comes from Cormorant Asset Management, Rock Springs Capital, Mountain Group Partners, NEA, Hatteras Venture Partners, AstraZeneca, Johnson & Johnson Innovation, Syno Capital and Fletcher Spagt Ventures.

"[With] PB1046 and future product candidates based on our elastin-like polypeptide ("ELP") technology, PhaseBio has the potential to build a significant pipeline in the orphan disease space," said Clay Thorp, PhaseBio’s executive chairman and general partner at Hatteras.

PhaseBio zeroed in on cardiopulmonary indications because "we had to focus someplace," Mow said. In fact, it licensed PB2542 because of its applications in that area. That said, the company aims to apply its platform to orphan diseases and not just those of cardiopulmonary nature.

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