RAPT Therapeutics Postpones $86 Million IPO

South San Francisco-based RAPT Therapeutics announced it is postponing its initial public offering (IPO) it filed earlier to raise $86 million via selling 5 million shares at $14 to $16 per share. No reasons were given for the postponement.

In May, the company changed its name from FLX Bio to RAPT Therapeutics to more accurately represent its focus on oral small molecule therapies. The company was founded in 2015 and since its founding has discovered and advanced two drug candidates that target CCR4.

FLX475 is the company’s lead oncology drug. It selectively inhibits the migration of regulatory T cells (Treg) into tumors. In a Phase I clinical trial in 104 healthy volunteers, the therapy was well tolerated and showed favorable drug-like properties and target engagement. It is currently in a Phase I/II trial as a monotherapy and in combination with Merck’s Keytruda (pembrolizumab) in patients with “charged” tumors. The company expects proof-of-concept data in the first half of 2020.

Its other lead product is RPT193, which selectively inhibits the migration of type 2 T helper cells (Th2) into tissues inflamed by allergic reactions. These types of Th2 are drivers of diseases like atopic dermatitis, asthma, chronic urticaria (skin rash), allergic conjunctivitis, rhinosinusitis and eosinophilic esophagitis. In preclinical models, RPT193 reduced inflammation comparable with leading injectable biologics.

On June 18, RAPT completed a $37 million Series C extension. The financing round included funds and accounts advised by T. Rowe Price Associates, and existing investors The Column Group, GV (formerly Google Ventures), Kleiner Perkins, Topspin Partners, and Celgene Corporation.

“We continue to advance our pipeline of oral small molecule therapeutics, with proof-of-concept results expected in the first half of 2020 from our FLX475 program targeting multiple cancers and in mid-2020 from our RPT193 program in atopic dermatitis,” stated Brian Wong, president and chief executive officer of RAPT, at the time. “We appreciate the belief in our vision to use our immunology-based drug discovery and development engine to bring new therapeutics to patients in need of safe and effective treatment options, both in cancer and in inflammatory disease.”

In May, RAPT entered into a research deal to use Personalis’ universal cancer immunogenomics platform, ImmunoID NeXT, to study therapy-related changes in advanced cancer patients taking part in a Phase I/II clinical trial of FLX475.

ImmunoID NeXT consolidates multiple biomarker assays, allowing for the analysis of about 20,000 genes in both DNA and RNA in a single sample. RAPT plans to compare pre- and post-treatment tumor biopsy samples to get a more comprehensive understanding of treatment-related changes in the tumors. RAPT also plans to use the technology platform to evaluate levels of several inflammation-related and immune cell type-related markers in its ongoing Phase II clinical trials of FLX475.

“Using the ImmunoID NeXT Platform for our FLX475 studies will help confirm its mechanism of action and demonstrate that inhibiting the CCR4 receptor with FLX475 blocks the migration of regulatory T-cells (Treg) into tumors,” Wong said at the time. “With this cutting-edge platform, we may be able to show that FLX475, by blocking Treg migration, decreases immune suppression and stimulates an immune response against cancer cells in the tumor microenvironment.”