Preliminary Retifanlimab Results Positive For Advanced Anal Squamous Carcinoma

Author: By Lynda Williams, Senior medwireNews Reporter 

medwireNews: Patients with locally advanced or metastatic squamous carcinoma of the anal canal (SCAC), including those with HIV infection, may derive benefit from retifanlimab therapy, suggest POD1UM-202 trial findings reported at the ESMO Virtual Congress 2020. 

Retifanlimab is an immunoglobulin G4 antibody against PD-1 that has shown preliminary activity against solid tumours including cervical cancer, which like SCAC is an HPV-driven malignancy, explained presenting author Sheela Rao, from The Royal Marsden in London, UK. 

The phase II open-label study included 94 patients, aged a median of 64 years, who had received up to two lines of systemic treatment including platinum-based chemotherapy and/or radiotherapy. Nine patients were HIV positive and undergoing highly active antiretroviral therapy with an undetectable viral load and a CD4+ count of at least 300 cells/µL. 

Patients were given retifanlimab 500 mg intravenous infusion every 28 days for up to 2 years and followed up for a median of 7.1 months. 

The primary endpoint of overall response rate by independent central review was 13.8%, including a complete response in one patient and a partial response in 12.8%. A further 35.1% of patients had stable disease, giving a disease control rate of 48.9%.  

Sheela Rao described the median response duration of 9.5 months as being “meaningful” and noted that “responses were seen regardless of age, sex, HIV status, metastatic liver disease and PD-L1 expression”. 

Median progression-free survival was 2.3 months, while the median overall survival was an “impressive” 10.1 months for the refractory setting of this disease, the presenter remarked. 

Treatment-related adverse events (AEs) occurred in 58.5% of patients and at grade 3 or more severe in 11.7% but just 4.2% discontinued treatment because of these AEs. Immune-related AEs occurred in 25.5% of patients, including at grade 3 or worse in 6.4%, and led to discontinuation in 2.1%. 

Of note, retifanlimab’s safety profile was “as expected” and the PD-1 inhibitor was “well tolerated” by the HIV-positive patients, none of whom lost control of their infection, the presenter said. 

Discussing the findings, Sheela Rao said the “overall response rate of 14% is certainly comparable to that seen with other PD-1 inhibitors in metastatic anal cancer as well as other HPV-related malignancies”, adding that “the median duration of response of 9.5 months compares favourably to historical experience with previous chemotherapy”. 

She therefore concluded: “As such, these results warrant further investigation of retifanlimab in phase III trials, as a potential new therapeutic option for squamous cell cancer of the anus. 

“A phase III trial [POD1UM-303] is already underway in the first-line setting evaluating [retifanlimab in combination with] carboplatin and paclitaxel in patients with inoperable locally recurrent or advanced anal cancer.” 

Reference 

Rao S, Capdevila J, Gilbert D, et al. POD1UM-202: Phase II study of retifanlimab in patients (pts) with squamous carcinoma of the anal canal (SCAC) who progressed following platinum-based chemotherapy. Ann Oncol 2020; 31 (suppl_4): S1142–S1215. DOI:10.1016/annonc/annonc325.