Italian report of expanded access for nab-sirolimus in patients with malignant perivascular epithelioid cell tumor (PEComa)

e23541 Background: Malignant perivascular epithelioid cell tumor (PEComa) is a rare aggressive sarcoma, with no approved treatment in Europe, while the mechanistic target of rapamycin (mTOR) inhibitor nab-sirolimus has been approved in US. In Europe, an expanded access program is available for patients with advanced or metastatic PEComa. Methods: We retrospectively collected data of patients with advanced/metastatic PEComa treated at our institution from December 2020 through 3 rd February 2023 with nab-sirolimus. Nab-sirolimus was administered as an intravenous infusion over 30 minutes at a dosage of 100 mg/m2 on days 1 and 8 of each 21-day cycle. Results: At the time of this analysis, 10 patients were treated with nab-sirolimus and 8 are evaluable for response. Of them, 4 patients received nab-sirolimus as their first mTOR inhibitor therapy, while 4 had already received another mTOR inhibitor, being discontinued for PD. Amongst patients not pretreated with mTOR inhibitors, 2/4 had a PR as their best response, 1/4 obtained SD and 1/4 obtained PD. Amongst patients pretreated with another mTOR inhibitor, all but 1 obtained PD as their best response and 1/4 had SD. The majority of nab-sirolimus-related adverse events were grade 1 or 2 and were manageable for long-term treatment. No grade 4 treatment-related adverse events were observed. Amongst the 10 patients treated with nab-sirolimus, tumor profiling is available for 6 patients, being ongoing for the other 4. Conclusions: nab-Sirolimus is active in patients with malignant PEComa. Activity is mainly confined to those not already treated with other mTOR inhibitors.