Abstract B011: Phase 2, multicenter, open-label basket trial of nab-sirolimus for malignant solid tumors harboring pathogenic inactivating alterations in TSC1 and TSC2 (PRECISION I)

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Abstract Introduction/objective: PRECISION I (NCT05103358) is an ongoing trial of nab-sirolimus in advanced cancers harboring pathogenic inactivating alterations in TSC1 or TSC2. TSC1 and TSC2 alterations have been observed in patients with various cancers, including the most common cancer of the female reproductive organs, endometrial cancer, where ~3% contain TSC1 and/or TSC2 alterations. nab-Sirolimus, approved in the USA for patients with advanced malignant perivascular epithelioid cell tumor (PEComa), is an albumin-bound mTOR inhibitor (mTORi) that inhibits the mTOR pathway via suppression of the mTORC1 complex. When TSC1 or TSC2 is inactivated via mutation or loss, the mTOR pathway may be aberrantly activated. In an exploratory analysis of AMPECT (NCT02494570), a pivotal trial of nab-sirolimus in advanced malignant PEComa, 64.3% (9/14) of patients with pathogenic inactivating TSC2 or TSC1 alterations had a confirmed response. Most treatment-related adverse events in AMPECT were grade 1/2 (none were grade ≥4) and were consistent with mTORi-class adverse events. Based on the clinical observations from AMPECT and the underlying mechanism of action of nab-sirolimus, the PRECISION I trial was designed to assess the safety and efficacy of nab-sirolimus in a tumor-agnostic study of patients with advanced cancers with TSC1 or TSC2 inactivating alterations. Patients with endometrial cancer are expected to be enrolled based on the frequency of TSC1 and TSC2 inactivating alterations. Methods: Eligible patients are ≥12 years old and mTORi-naïve, possess advanced or metastatic malignant solid tumors with TSC1 or TSC2 inactivating alterations identified using next-generation sequencing (NGS) in tumor tissue or liquid biopsy (confirmed by central review of NGS reports), and have received appropriate standard treatments, per investigator. nab-Sirolimus 100 mg/m2 is given intravenously over 30 min on days 1 and 8 of each 21-day cycle. The primary endpoint is overall response rate per independent radiographic review (IRR) using Response Evaluation Criteria in Solid Tumors v1.1. Other endpoints include duration of response, time to response, progression-free survival by IRR, overall survival, patient-reported quality of life, and safety. Trial Status: Enrollment began in March 2022 and is expedited through collaboration with leading NGS providers; ongoing study access is facilitated through a just-in-time approach to trial location activation. Citation Format: Debra L. Richardson, Gopa Iyer, Li Ding, Anita N. Schmid, Willis Navarro, David Kwiatkowski, Jordi Rodon Ahnert. Phase 2, multicenter, open-label basket trial of nab-sirolimus for malignant solid tumors harboring pathogenic inactivating alterations in TSC1 and TSC2 (PRECISION I) [abstract]. In: Proceedings of the AACR Special Conference on Endometrial Cancer: Transforming Care through Science; 2023 Nov 16-18; Boston, Massachusetts. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(5_Suppl):Abstract nr B011.