RAPT Therapeutics Announces Late-Breaking Oral Presentation of Positive Results from Phase 1b Trial of RPT193 at the 30th European Academy of Dermatology and Venereology Congress

• Benefit demonstrated in all key exploratory efficacy endpoints - EASI, EASI-50, EASI-75, EASI-90, vIGA, BSA and pruritus NRS-3 and 4 - with once-daily, oral treatment with RPT193
  
• Continued improvement observed 2 weeks after end of treatment on multiple endpoints

SOUTH SAN FRANCISCO, Calif., Sept. 30, 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 that positive topline results from its randomized placebo-controlled Phase 1b clinical trial of RPT193 as monotherapy in 31 patients with moderate-to-severe atopic dermatitis (AD) were presented at the European Academy of Dermatology and Venereology (EADV) Congress by Robert Bissonnette, M.D., FRCPC. Dr. Bissonnette is a board-certified dermatologist and currently serves as president of the board of directors of the International Eczema Council. He is also chief executive officer and medical director of Innovaderm Research Inc., a contract research organization that specializes in conducting clinical studies in dermatology.

“These Phase 1 results strongly support the potential of RPT193 as an effective once-daily, oral treatment for atopic dermatitis with a clean safety profile,” said Brian Wong, M.D., Ph.D., President and CEO of RAPT Therapeutics. “RPT193 demonstrated impressive improvements in measures of disease severity, including vIGA and EASI-75, which are the approvable endpoints in the US and Europe. The magnitude and extended clinical benefits observed even after dosing cessation are especially intriguing and warrant further investigation. We look forward to initiating our Phase 2b clinical trial in atopic dermatitis and to expanding our exploration of RPT193 in a Phase 2a trial in asthma.”

The Phase 1b trial results demonstrated that at Day 29 after end of treatment, clear benefit over placebo was observed on Eczema Area and Severity Index (EASI) score, EASI-50, vIGA 0/1 (clear or almost clear skin), body surface area (BSA), and pruritis NRS-3 and 4 (3 and 4 point reduction on the numerical rating scale for itch). By the end of study, including the two-week follow-up period (Day 43), RPT193 demonstrated continued improvement in the EASI, EASI-50, EASI-75, EASI-90, vIGA 0/1, and BSA. In a post-hoc statistical analysis comparing RPT193-treated patients to placebo-treated patients, statistically significant improvements in EASI, EASI-50 and BSA were observed at Day 43. RPT193 was well tolerated in the Phase 1b study. No serious adverse events were reported, and all adverse events reported were mild or moderate in intensity.

“These early-stage clinical results for RPT193 are very promising and demonstrate its potential as an attractive, differentiated treatment for atopic dermatitis,” said Dr. Bissonnette. “Further improvement after cessation of dosing could be consistent with unique kinetics associated with the mechanism of action of RPT193 and its unique design in targeting Th2 cell migration and function.”

About the Phase 1a/1b Study of RPT193
The Phase 1b study reported today was part of RAPT’s first-in-human Phase 1a/1b trial of RPT193. The Phase 1b portion of the trial was a randomized, double-blind, placebo-controlled study examining RPT193 as monotherapy in patients with moderate-to-severe AD. The study was conducted at multiple sites in the United States and enrolled 31 patients with moderate-to-severe AD who had an inadequate response to, or were intolerant of, topical corticosteroids. The primary endpoint of the Phase 1b study was safety. Secondary and exploratory endpoints included pharmacokinetics, biomarkers and clinical efficacy as evaluated by multiple measurements, including percent change in the Eczema Area and Severity Index (EASI) score, change in body surface area (BSA) affected by AD, the validated Investigator Global Assessment (vIGA) and pruritus 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.

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. Preclinical data suggest that RPT193 also has the potential to modulate Th2 cell function by lowering the secretion of Th2 cytokines upon stimulation. 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 highly prevalent 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 is a marketed injectable product 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. There are ~19M adults and ~10M children affected by AD in the US.

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, RAPT 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. RAPT 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 interpretations of the topline results from the Phase 1b clinical trial of RPT193, clinical development progress including the anticipated advancement of RPT193 to a Phase 2b trial in atopic dermatitis as well as Phase 2 trials in other indications 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 Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission on August 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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