Emerging and Experimental Agents for Anal Cancer: What is New?

Squamous cell carcinoma of the anal canal (SCCA) is an HPV-related malignancy with rising incidence in the past few decades in the US, characterized by high rates of complete response to chemoradiotherapy with curative intent. However, in a long-term follow-up, a meaningful subgroup of patients with locally advanced disease presents disease recurrence, which demands treatments with high morbidity and important impact in the quality of life. In metastatic or unresectable disease, palliative chemotherapy is the standard of care, but it is still associated with a dismal prognosis. Novel agents are urgently needed in the systemic therapy of SCCA. From a translational standpoint, there are many hurdles to overcome, since mutation is the most frequent genetic abnormality and actionable mutations are rarely found in SCCA, as well as it is characterized by low tumor mutational burden and low rates of high-frequency microsatellite instability. But the latest studies of immunotherapeutic approaches have produced promising findings and this therapeutic strategy is the major path being followed in the ongoing clinical trials. The latest advances in the systemic therapy of SCCA have provided the framework for the conception of new clinical trials. Therefore, carboplatin plus paclitaxel have become the backbone for novel agents. Immune checkpoint inhibitors (ICIs), mainly anti-PD-1 monoclonal antibodies, such as retifanlimab, nivolumab, and atezolizumab have been studied in Phase III trials with chemotherapy in first-line therapy. Likewise, ICIs have been evaluated in locally advanced and refractory disease. Novel technologies, such as bispecific antibodies, and immunotherapeutic approaches, such as vaccines and adoptive T-cell therapies, have also been tested in ongoing clinical trials. Immunotherapy may bring practice-changing advances in the systemic therapy of SCCA in the next few years and it might play a larger role in the therapeutic management of this challenging disease.