Phase I Study of Lenalidomide Combined with Dose-Adjusted EPOCH and Rituximab (EPOCH-R²) in Primary Effusion Lymphoma in Participants with or without HIV (NCT02911142)

Background: Primary effusion lymphoma (PEL) is a rare, aggressive B-cell neoplasm strongly associated with HIV infection. It generally presents with malignant effusions but may also present with extracavitary (EC) masses. It is caused by the gammaherpesvirus Kaposi sarcoma herpesvirus (KSHV, also called human herpesvirus 8), which is also responsible for the development of Kaposi sarcoma (KS) and a form of multicentric Castleman disease (MCD). There are no prospective studies in PEL and no standard therapy. Prognosis is poor compared to other HIV-associated lymphomas with median survival of 10-22 months when treated with conventional lymphoma chemotherapy regimens. In vitro data demonstrate lenalidomide (LEN), an immunomodulatory agent, downregulates IRF4, a cell activation marker overexpressed in PEL, and can reverse KSHV-induced downregulation of MHC-1 and ICAM-1. Dose-adjusted infusional etoposide, vincristine, and doxorubicin with cyclophosphamide and prednisone combined with rituximab (EPOCH-R) has been shown to be safe and effective for CD20⁺ HIV-associated lymphomas. While PEL is generally CD20 negative, rituximab eradicates the KSHV-infected B-cell reservoir, a source of inflammatory cytokines that drive the natural history of PEL; moreover, many patients have concurrent MCD for which rituximab is a standard treatment.

Methods: In a prospective phase 1/2 study conducted in the HIV and AIDS Malignancy Branch at the National Cancer Institute (NCI), we are evaluating EPOCH combined with rituximab and LEN (EPOCH-R²) in participants (pts) with untreated PEL. The primary objective was to evaluate safety and tolerability of EPOCH-R² and determine the recommended phase 2 dose (RP2D) of LEN. PEL was diagnosed/confirmed in the NCI Laboratory of Pathology via cytology and/or flow cytometry of effusions or via biopsy in EC disease. Pts received EPOCH-R days 1-5 and every 21 days for 6 cycles. LEN was administered orally days 1-10 of each cycle starting at 25 mg (with dose de-escalation if toxicity occurred). Dose-limiting toxicities were evaluated during cycles 1-2. Pts with leptomeningeal PEL (CSF-PEL), determined by cytology and/or flow cytometry of cerebrospinal fluid, received intrathecal chemotherapy; intrathecal prophylaxis was given to pts without CSF-PEL. All pts received thromboprophylaxis (aspirin 81 mg daily), opportunistic infection prophylaxis, and antiretroviral therapy (ART). Adverse events (AEs) were evaluated using CTCAEv5 and treatment response was evaluated by Lugano criteria after cycles 2 and 6. Response to treatment, immune reconstitution, and overall survival (OS) were evaluated using descriptive statistics, Wilcoxon signed-rank test and Kaplan-Meier methodology.

Results: We are reporting results of the completed Phase I portion of the trial. 6 HIV⁺ cisgender men (5 Black, 1 White) with stage 4 PEL were enrolled July 2017-August 2019. All received non-boosted integrase inhibitor-based ART. 3 had pleural effusions, 2 had EC disease without effusions, and 1 had both effusions and EC disease. 3 had CSF-PEL and 1 had bone marrow involvement. 4 had concurrent KS; 1 also had concurrent MCD. Median CD4⁺was 231 cells/µL (IQR: 10, 310) at baseline and 189.5 cell/µL (IQR: 56, 224) at end-of-treatment, which was not a significant decline (p=0.46). The most common AEs were hematologic, including grade (G) 4 neutropenia (100%), leukopenia (100%), thrombocytopenia (67%) and CD4⁺ lymphopenia (67%). 3 pts (50%) developed G3 pulmonary emboli despite thromboprophylaxis. There were 7 episodes of G3 febrile neutropenia and 2 episodes of sepsis. No pts developed opportunistic infections. There were no dose-limiting toxicities and LEN 25 mg is the RP2D. 4 pts completed all 6 cycles. 2 pts completed 5 cycles: 1 died due to progressive disease and 1 had progressive disease and went on to receive additional therapy. 1 pt who completed all 6 treatment cycles died due to HIV-related complications 5 months after EPOCH-R² with no evidence of PEL at autopsy. The response rate was 83.3% (95% CI: 36.8-99.6) and 50% (95% CI: 11.8-88.1) after cycles 2 and 6, respectively. 2-year overall survival was 66.7% (95% CI:19.5-90.4).

Conclusions: Front-line PEL treatment with EPOCH-R² is safe, and the most common toxicities were hematologic. This regimen showed preliminary evidence of activity and good OS, which will be further evaluated in the ongoing phase 2.

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