Sickle cell biotech GBT banks $120M in an above-range IPO

Third Rock Ventures startup Global Blood Therapeutics ($GBT) raised $120 million in an IPO, pricing above its expected range and picking up the cash it needs to advance an oral treatment for sickle cell disease.

The South San Francisco company moved 6 million shares at $20 apiece, besting its projection of $16 to $18, and set aside another 900,000 shares to cover overallotments. If GBT's underwriters pick up their options on the extra shares, the biotech could gross nearly $140 million in its offering.

With the proceeds, GBT plans to push forward with GBT440, an oral treatment designed to interrupt the root cause of sickle cell disease. Healthy red blood cells become sickled when their hemoglobin fuses together into long, sharp strands, leading to cell malformation that can cause deadly blockages in vessels. GBT440 works by binding to those hemoglobin molecules before they can stick together, encouraging them to oxidize and thereby reducing the chances that they sickle, according to the company.

The drug is now in a Phase I/II study, began in December, and GBT is planning to enroll up to 128 patients to establish GBT440's safety before expanding into an efficacy trial. The study is slated to conclude in May, according to, after which GBT plans to meet with regulators and plot a path forward.

Beyond its lead candidate, the company is at work on an early-stage oral treatment for hereditary angioedema, a rare disorder that results in dangerous bodily swelling.

GBT is a product of Third Rock's startup engine, through which the firm gathers talent around a promising technology and bankrolls early development. GBT got off the ground with a $40 million Series A in 2012 and raised $48 million more in January.

Meanwhile, biotech's record first-half pace of IPOs has continued through the summer. Over the past few weeks alone, Aimmune Therapeutics ($AIMT), Zynerba Pharmaceuticals ($ZYNE) and Intec Pharma ($NTEC) have pulled off market debuts. And the queue of companies looking to do the same continues to grow, with Adynxx, Gensight Biologics and Erytech all lining up for IPOs of their own.

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