Background: Albumin-bound (nab)-sirolimus, a novel mTOR inhibitor (mTORi) that utilizes nanoparticle technology to preferentially target tumors, is approved in the US for the treatment of adults with malignant PEComa. In an exploratory analysis of the AMPECT registrational trial of nab-sirolimus in advanced malignant PEComa (NCT02494570), 8/9 (89%) and 1/5 (20%) patients with TSC1 and TSC2 inactivating alterations, respectively, had confirmed response (Wagner, J Clin Oncol. 2021). Importantly, both TSC1 and TSC2 alterations have been observed in patients with various gastrointestinal cancers (Table). Overall, most treatment-related adverse events (TRAEs) in AMPECT were grade 1/2 and manageable for long-term treatment; no grade ≥4 TRAEs occurred. Methods: PRECISION I (NCT05103358) is a phase 2, open-label, multi-institutional basket trial evaluating efficacy and safety of nab-sirolimus in patients with alterations in TSC1 (Arm A) and TSC2 (Arm B). Patients ≥12 years old with malignant solid tumors harboring pathogenic inactivating alterations in TSC1 or TSC2 (confirmed by central review of next generation sequencing reports) who have progressed on standard therapies and are mTORi-naïve are eligible. nab-Sirolimus 100 mg/m² will be administered weekly as an intravenous infusion over 30 minutes on Days 1 and 8 of each 21-day cycle. The primary endpoint is overall response rate determined by independent review using RECIST v1.1; other endpoints include duration of response, disease control rate, time to response, progression-free survival by independent radiographic review, overall survival, patient-reported quality of life, and safety. Enrollment is ongoing. The most frequent tumor types expected in this tissue-agnostic trial are bladder, hepatobiliary, endometrial, soft tissue sarcoma, ovarian, and esophagogastric based on the prevalence of TSC1 or TSC2 alterations (Table). Clinical trial information: NCT05103358.

All gastrointestinal tumors (bolded) with known incidence of TSC1/TSC2, and tumor types with combined incidence of TSC1/TSC2 alterations of >2% are listed. ^aThe proportion of patients with definite impact mutations (ie, mutations known to have a biological impact; this includes frameshift, nonsense, and splice-site mutations and deep deletions) was derived from the NIH NCI Genomic Data Commons Data Portal (NIH NCI Genomic Data Commons).