RAPT Therapeutics Completes Enrollment in Phase 1b Trial of RPT193 in Atopic Dermatitis

Company Reaffirms Guidance to Report Data in 1H 2021

SOUTH SAN FRANCISCO, Calif., March 22, 2021 (GLOBE NEWSWIRE) — RAPT Therapeutics, Inc. (Nasdaq: RAPT), a clinical-stage, immunology-based biopharmaceutical company focused on discovering, developing and commercializing oral small molecule therapies for patients with significant unmet needs in oncology and inflammatory diseases, today announced enrollment has been completed in its Phase 1b clinical trial of RPT193 in patients with moderate to severe atopic dermatitis (AD). The Company expects treatment follow up and data compilation to be completed in time for top line results to be reported in the first half of 2021.

“We look forward to reporting top line data from this trial of RPT193 in atopic dermatitis, which could serve as initial proof of concept in AD and a wide range of inflammatory diseases,” said Brian Wong, M.D., Ph.D., President and CEO of RAPT Therapeutics. “We believe an encouraging outcome in this Phase 1b trial would be if RPT193 shows a clear benefit compared to placebo in at least one key clinical or patient-reported endpoint. Evidence of efficacy, combined with once-daily oral convenience and a favorable safety profile, would be attractive in this patient population. This is an exciting time for RAPT as our CCR4 antagonist platform may potentially demonstrate broad clinical utility in both oncology and inflammation.”

RAPT’s Phase 1b study is part of a first-in-human Phase 1a/1b trial of RPT193. The Phase 1b portion of the trial is a randomized, double-blind, placebo-controlled study in patients with moderate to severe AD. The study is being conducted at multiple sites in the United States and has enrolled 31 patients. The primary endpoint of the Phase 1b study is safety. Secondary and exploratory endpoints include pharmacokinetics, biomarkers and clinical efficacy as evaluated by multiple measurements, including the Eczema Area and Severity Index (EASI) and pruritis Numerical Rating Scale (NRS). The Phase 1b trial was not powered to achieve statistical significance for any particular endpoint.

The Phase 1a portion of the Phase 1a/1b trial was a standard single and multiple dose escalation study in healthy volunteers. The data from the Phase 1a study demonstrated pharmacokinetics and pharmacodynamics that support once-daily oral dosing with RPT193, and blinded safety data supported initiation of the Phase 1b portion of the trial. Preclinical studies of RPT193 have demonstrated its ability to block the migration of mouse and human Th2 cells in vitro as well as inhibit inflammation in models of atopic dermatitis and asthma.

About RPT193
RPT193 is a small molecule oral therapy in development for the treatment of atopic dermatitis and other inflammatory diseases. RPT193 is designed to selectively inhibit the migration of Th2 cells into inflamed tissues by blocking CCR4, a receptor highly expressed on Th2 cells. In allergic inflammatory diseases such as AD, chemokines recruit Th2 cells via CCR4 into inflamed tissues, where the Th2 cells secrete proteins known to drive the inflammatory response. The role of Th2 cells has been clinically validated by injectable biologics targeting this pathway. Patients with atopic dermatitis express higher levels of CCR4 ligands compared with healthy humans; these ligands also correlate with the severity of disease. RAPT believes that by inhibiting CCR4, RPT193 has the potential to bring therapeutic benefit to patients across a broad spectrum of inflammatory diseases, including atopic dermatitis, asthma, chronic urticaria, allergic rhinitis, chronic rhinosinusitis and eosinophilic esophagitis.

About Atopic Dermatitis
Atopic dermatitis is a chronic, inflammatory skin disease characterized by skin barrier disruption and immune dysregulation. Patients with AD have chronically inflamed skin lesions that can cause debilitating pruritus (itch), which can severely impair quality of life. While there are marketed injectable products for the treatment of AD, RAPT believes RPT193, if approved, could fill an unmet medical need for the treatment of inflammatory disorders with the convenience of once daily oral dosing.

About RAPT Therapeutics, Inc.
RAPT Therapeutics is a clinical stage immunology-based biopharmaceutical company focused on discovering, developing and commercializing oral small molecule therapies for patients with significant unmet needs in oncology and inflammatory diseases. Utilizing its proprietary discovery and development engine, the Company is developing highly selective small molecules designed to modulate the critical immune drivers underlying these diseases. RAPT has discovered and advanced two unique drug candidates, FLX475 and RPT193, each targeting C-C motif chemokine receptor 4 (CCR4), for the treatment of cancer and inflammation, respectively. The Company is also pursuing a range of targets that are in the discovery stage of development.

Forward-Looking Statements
This press release contains forward-looking statements. These statements relate to future events and involve known and unknown risks, uncertainties and other factors that may cause our actual results, performance or achievements to be materially different from any future performances or achievements expressed or implied by the forward-looking statements. Each of these statements is based only on current information, assumptions and expectations that are inherently subject to change and involve a number of risks and uncertainties. Forward-looking statements include, but are not limited to, statements about the timing of the Phase 1b clinical trial of RPT193, interpretations of possible outcomes from that trial and the potential of RPT193 to treat atopic dermatitis or other inflammatory diseases. Detailed information regarding risk factors that may cause actual results to differ materially from the results expressed or implied by statements in this press release may be found in RAPT’s Annual Report on Form 10-K filed with the Securities and Exchange Commission on March 11, 2021 and subsequent filings made by RAPT with the Securities and Exchange Commission. These forward-looking statements speak only as of the date hereof. RAPT disclaims any obligation to update these forward-looking statements.

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