Bui, Nam

TPS11592 Background: Epithelioid hemangioendothelioma (EHE) is an ultra-rare vascular sarcoma with about 120 cases diagnosed in the US per year. Although it is commonly considered an indolent disease, in its aggressive form clinical outcomes are poor. Molecularly, EHE is characterized by the presence of oncogenic fusions with HIPPO pathway effectors TAZ or YAP; TAZ-CAMTA1 or YAP-TFE3. YAP/TAZ are modulators of mTORC1 in preclinical models, suggesting that mTOR inhibition may be an effective treatment mechanism for EHE. Nab-sirolimus is albumin bound sirolimus, which achieves higher intratumoral accumulation compared to oral sirolimus and has demonstrated increased antitumor activity in preclinical cancer models compared to the oral mTOR inhibitors sirolimus and everolimus. This is an open label, multi-center, single arm, phase II clinical trial with a two-stage design, testing nab-sirolimus for progressing or symptomatic EHE. The primary objective is to determine ORR of nab-sirolimus in patients with EHE who require systemic treatment. We hypothesize that nab-sirolimus will have significant clinical efficacy for EHE as measured by the primary endpoint of objective response rate, as well as by secondary outcomes including progression free survival benefit over historical controls and by improvement in patient reported outcomes (PROs). If positive, this trial could lead to a new standard of care for treating EHE. Methods: This is a single arm, multi-center, phase 2 study with a two-stage design. Key inclusion criteria include histologically or cytologically confirmed EHE that is either progressing or clinically symptomatic, not a candidate for curative intent surgery, and requires systemic therapy in the opinion of the investigator, radiographically evaluable disease by RECIST v1.1, age ≥18 years, ECOG performance status ≤ 2, and adequate end organ function. With a Simon two-stage optimal design with one sided alpha 0.10, power 90%, assuming a historical control ORR 5% to detect an ORR of 20% (alternative hypothesis), 12 patients will be included in the first stage. If there is ≥ 1 response, an additional 25 patients will be enrolled to a total of 37 patients. ≥ 4 responses are needed for a significant result. The total planned accrual is 41 patients to account for unevaluable patients who may be enrolled, 10% above the required evaluable patients. Planned post hoc subgroup analyses will include outcomes by fusion type and presence of serosal effusions at the time of study enrollment. The trial is registered at clinicaltrials.gov NCT07104331. Clinical trial information: NCT07104331 .

11502 Background: To report results from the open-label alveolar soft part sarcoma (ASPS) cohort of the phase III APROMISS trial (NCT03016819) evaluating Catequentinib hydrochloride (AL3818), an oral multitargeted receptor tyrosine kinase inhibitor, in adults with advanced or metastatic ASPS. Methods: Adult patients with pathologic and molecularly confirmed advanced ASPS, either treatment-naive or previously treated (excluding cediranib), were enrolled in the open-label, non-randomized ASPS cohort of the phase III APROMISS trial conducted across the United States, Asia, and Europe. Catequentinib hydrochloride was administered orally at 12 mg once daily in 21-day cycles (14 days on/7 days off) until disease progression, toxicity, or death. The primary endpoint was objective response rate (ORR) assessed per RECIST by Blinded Independent Central Review (BICR) (predefined threshold: 31%). Secondary endpoints included duration of response (DOR) with a predefined target of =/>6 months, progression free survival (PFS) and overall survival (OS). Results: From July 2017 to August 2022, a total of 56 patients entered the trial; 56 patients were evaluable for the primary endpoint. Median (m-) age was 29.5 years (range: 18 – 66), with 24 female and 32 male. Best overall response included 1/56 complete response (1.8%), 14/56 partial responses (25.0%), 36/56 stable disease (64.3%), and 3/56 (5.4%) progressive disease. RECIST ORR by BICR was 26.8% (95% CI, 15.8–40.3); m-DOR was 22.57 months (95%CI: 10.38-NE). The study data was collected close to 8 years for all patients. mPFS was 18.33 months (95% CI, 14.19–23.13), with 6- and 12-month progression-free rates of 88.77% (95% CI, 76.68–94.79) and 65.54% (95% CI, 50.42–77.06), respectively. mOS was 59.27 months (95% CI, 44.09–NE), with 6- and 12-month overall survival rates of 94.64% (95% CI, 84.30–98.24) and 90.81% (95% CI, 79.30–96.08), respectively. Overall, 27/56 (48.2%) patients experienced grade ≥3 treatment-related adverse events, most commonly diarrhea (50.0%), hypertension (44.6%), fatigue (37.5%), nausea (35.7%), and palmar-plantar erythrodysesthesia syndrome (30.4%); one patient (1.8%) had a grade 5 event (respiratory failure). Conclusions: Catequentinib hydrochloride demonstrated meaningful antitumor activity and durable responses in adults with advanced ASPS. Despite the ORR of 26.8% slightly below the predefined 31% threshold, disease control was prolonged, with a m-DOR exceeding 22 months. Favorable PFS and OS outcomes, together with a manageable safety profile, support its clinical benefit in this ultra-rare sarcoma. Clinical trial information: NCT03016819 .