Phase I study of BJ-001, a tumor-targeting interleukin-15 fusion protein, in patients with solid tumor.
Authors: Ki Y. Chung, Haeseong Park, Raghad Muhsin Abdul-Karim, Deborah Blythe Doroshow, Jorge Chaves, Teresa A. Coleman, Keiko Nakai, Pankaj Patel, John Wang, Haizhou Zhang, Leijun Hu
Journal: Journal of Clinical Oncology (2021)

e14545 Background: BJ-001 is the first tumor-targeting Interleukin-15 (IL-15) fusion protein, composed of an integrin-binding Arg-Gly-Asp (RGD)-4C motif, linked with a human IgG1 Fc, and then a modified sushi domain of human IL-15Rα unit and a human IL-15. Tumor-targeting is achieved with RGD-4C motif which binds to αvβ3, αvβ5, and αvβ6 integrins, commonly overexpressed in solid tumors. The molecule has shown an ability to activate Natural Killer (NK) and T cells in vitro and in pre-clinical in vivo studies. Methods: This first in-human (FIH) study has 2 phases: Phase 1a and Phase 1b. Phase 1a consists of 3 parts. In all 3 parts patients receive escalating doses of BJ-001 as a once weekly subcutaneous injection for 4 weeks in 6-week cycles. Part 1 utilizes an accelerated dose escalation design with single patient cohort for the first 3 dose levels. Part 2 uses a 3+3 dose escalation design. Part 3 uses a 3+3 dose escalation of BJ-001 but in combination with a fixed-dose PD-(L)1 inhibitor. Dose escalation will proceed based on clinical safety and tolerability data observed during the Dose Limiting Toxicity (DLT) period, i.e., Cycle 1 Days 1 through 28 for Part 1 and Cycle 1 Days 1 through 42 for Parts 2 and 3. Adult patients (ECOG PS ≤ 2) with locally advanced or metastatic solid tumors refractory to or intolerant of all existing therapies are eligible for Phase 1a. Phase 1b will enroll cohorts of adult patients with selected solid tumors known to have high levels of integrin expression at the Maximum Tolerated Dose or Recommended Phase 2 Dose of BJ-001 in combination with a PD-(L)1 inhibitor, as identified in Phase 1a, Part 3. Results: As of Jan 31, 2021, 9 patients have received BJ-001 dosing as a single agent at 0.21 µg/kg (n = 1), 0.9 µg/kg (n = 1), 3 µg/kg (n = 1), 6 µg/kg (n = 3), or 10 µg/kg (n = 3) in Phase 1a Parts 1 and 2, wherein 7 patients, including 1 patient in the 10 µg/kg cohort, have completed the DLT period. Among these 7 patients, 2 (1 in 3 µg/kg and 1 in 6 µg/kg cohorts) have stable disease and are still receiving BJ-001 treatment beyond Cycle 1. The longest duration in the study, to date, is approximately 4 cycles (over 5 months). Treatment Emergent Adverse Events (TRAEs) include injection site reactions (6/7, Grade 1-2), anorexia (2/7, Grade 1-2), cytokine release syndrome (1/7, Grade 1, resolved in 1 day), and temporal wasting (1/7, Grade 1). The AEs did not result in dose interruption or dose level adjustment. No DLTs observed to date. With escalating doses, a trend of increased post-dose NK cell counts observed, whereas Regulatory T cell (Treg) counts remained stable. Conclusions: To date, BJ-001 is well tolerated up to 6 µg/kg. The safety evaluation for 10 µg/kg is ongoing. The observed NK and Treg cell profiles are consistent with known IL-15 biology. Clinical trial information: NCT04294576.