Abstract
BACKGROUND: QBS10072S, is a L-type amino acid transporter 1 (LAT-1) targeted alkylating agent that utilizes LAT1 as both a transport and targeting mechanism. QBS10072S can cross the blood-brain barrier, exhibits potential for cytotoxicity with a mechanism distinct from temozolomide and has low off-target effects. QBS10072S is being evaluated in the Individualized Screening Trial of Innovative Glioblastoma Therapy (INSIGhT) trial (NCT02977780), a randomized phase 2 adaptive multi-arm platform trial. METHODS: Adult patients with newly diagnosed MGMT-unmethylated glioblastoma are eligible for INSIGhT. Since there is no safety data available for QBS10072S in combination with radiotherapy, a safety lead-in evaluation was conducted utilizing a 3 + 3 design. Starting dose for QBS10072S was 12mg/m(2) in combination with radiation therapy and adjuvantly as monotherapy in 28 day cycles. Patients were monitored for dose-limiting toxicities (DLTs) to identify the maximum tolerated dose and recommended phase 2 dose (RP2D). RESULTS: Nine patients were enrolled December 2022 to October 2023 for safety lead-in testing, and median age was 57 years (41-67) with 6 (66%) males, 6 (66%) patients with gross total resection, and median KPS 90 (range 80-100). Pharmacokinetic studies indicated that drug exposure was lower than prior studies, and three patients received 12mg/m(2), 15mg/m(2), and 18mg/m(2), respectively, per dose escalation protocol. No DLTs nor adverse events leading to study drug discontinuation were reported during the evaluation period. Four patients had possible treatment-related CTCAE grade ≥ 3 toxicity including lymphopenia (n=3) and fatigue (n=1). The RP2D was determined to be 18mg/m(2). Seven patients were discontinued from study treatment due to progressive disease and two patients remain on treatment. CONCLUSION: QBS10072S, concurrent and adjuvant to radiation therapy, was well-tolerated in patients with newly diagnosed unmethylated MGMT glioblastoma. QBS10072S 18mg/m(2) is being evaluated as a treatment arm in phase 2 testing in the ongoing INSIGhT trial.