KD025-208: A Phase 2a Study of KD025 for Patients with Chronic Graft Versus Host Disease (cGVHD) - Pharmacodynamics (PD) and Updated Results

Introduction cGVHD is characterized by an imbalance between effector and regulatory arms of the immune system that results in over production of IL-17 and IL-21. A reduction in the regulatory T (Treg) cells limits the ability of the immune system to re-calibrate this pro-inflammatory environment. KD025 is an oral Rho kinase 2 (ROCK2) selective inhibitor. In vitro data demonstrate KD025 modulates immune homeostasis by shifting the Th17/Treg balance towards Treg. Methods 3 cohorts (C1: 200 mg QD, C2: 200 mg BID, and C3: 400 mg QD) of patients (pts) with cGVHD after 1-3 prior lines of systemic therapy were treated in 28-Day cycles until disease progression. The primary endpoint is overall response rate (ORR) (partial/complete response) per 2014 NIH criteria. Additional endpoints include duration of response (DOR), corticosteroid (CS) dose reductions, Lee Symptom Scale (LSS) score and PD. Blood samples were collected at Cycle 1 Day 1 (C1D1), C2D1, C4D1 and C6D25, and shipped at ambient temperature. PBMC were isolated and kept frozen until analysis. Intracellular expression of IL-17A and FOXP3 was determined by flow cytometry. Results Data as of 6-June-2018 for C1 and C2 are included; C3 data will be available 4Q18. 17 and 16 pts were enrolled in C1 and C2 with median age 52 years, time from cGVHD diagnosis to KD025 treatment of 19 months, and 3 prior regimens. Median duration of treatment was37 (C1) and 33 (C2) weeks. KD025 demonstrated ORR of 65% in C1 and 63% in C2. Responses were rapid (76% at first assessment at 8 weeks) and durable (≥20 weeks) in 82% (C1) and 50% (C2) of responders. Median CS dose was reduced 44% (C1) and 26% (C2). 76% and 56% of pts achieved CS dose reductions. 5/33 (15%) pts discontinued CS. 65% (C1) and 50% (C2) achieved a meaningful improvement (≥7 point reduction) in the LSS score.  Common AEs were increased LFTs 42%, URI 33%, anemia 27%, nausea 24%, diarrhea 24% and fatigue 21%. Grade 3+ LFT increases were reported for 6 (18%) pts. 2 pts discontinued treatment due to AEs possibly related to KD025 (headache, diarrhea). SAEs were reported for 11/33 pts, none considered related to KD025. There was no apparent increased risk of infection. Exploratory PD analyses revealed an early increase in the percentage of CD4+ Treg cells by C2D1 with a simultaneous decrease in Th17 cells. The percentage of CD4+ Tregs continued to increase, and the Th17 cells continued to decrease through C6D25. Conclusion KD025 achieved responses with little toxicity. Responses are clinically meaningful with durability, reductions in CS doses and improvement in LSS score. PD data indicate KD025 may restore the Th17/Treg balance.