Case Report: Iparomlimab and Tuvonralimab-based therapy for epithelioid malignant peritoneal mesothelioma: a three-case series.

Background: Epithelioid malignant peritoneal mesothelioma (EMPM) is a rare and aggressive malignancy of serosal origin. Cytoreductive surgery combined with hyperthermic intraperitoneal chemotherapy is generally reserved for carefully selected patients in whom adequate cytoreduction appears feasible, while evidence supporting systemic immunotherapy remains limited for patients with unresectable disease or those unable to tolerate intensive treatment. Iparomlimab and tuvonralimab (QL1706) is a fixed-ratio anti-PD-1/anti-CTLA-4 MabPair formulation that has shown preliminary antitumor activity in several advanced solid tumors, but clinical experience in EMPM remains scarce. Case presentation: We retrospectively describe three patients with EMPM diagnosed through integrated clinicopathologic assessment who received QL1706 either as monotherapy or in combination with an antiangiogenic agent. Treatment response was assessed by the treating team on serial computed tomography (CT) using Response Evaluation Criteria in Solid Tumors version 1.1 (RECIST 1.1) as the evaluation framework. Results: Case 1 was a 53-year-old woman with a programmed death-ligand 1 (PD-L1) combined positive score (CPS) of 10. Diffuse peritoneal disease persisted after surgery and three sessions of postoperative catheter-based hyperthermic intraperitoneal chemotherapy. QL1706 plus bevacizumab subsequently produced stable disease with symptomatic improvement for approximately 7 months. Case 2 was an 89-year-old man with a PD-L1 CPS of 0 who was considered unsuitable for surgery or intensive chemotherapy. QL1706 plus dose-reduced lenvatinib achieved a partial response that remained ongoing for more than 10 months. Case 3 was a 70-year-old man with a PD-L1 CPS of 55 and pre-existing nephrotic syndrome. QL1706 monotherapy induced a rapid partial response, but treatment was discontinued because of worsening proteinuria and edema; the disease subsequently progressed, with a new intracranial lesion radiologically suspicious for metastasis. Conclusion: QL1706-based therapy achieved disease control in all three patients with EMPM who had limited conventional treatment options, including a durable response in an elderly patient with PD-L1-negative disease and rapid tumor regression with QL1706 monotherapy. The contrasting clinical courses suggest that overall benefit depends not only on tumor sensitivity but also on the accompanying treatment strategy and baseline organ function.