Avelumab and Merkel Cell Carcinoma: Causation and FDA Warning

From General Health to Pharmacovigilance

For decades, public health communication has centered on general wellness principles—balanced nutrition, routine screening, and awareness of environmental factors that influence disease. This broad foundation has served to educate populations about risk reduction without delving into the specific biological pathways of individual conditions. Within this legacy framework, the role of pharmaceutical interventions has been presented as a tool for treatment, with safety monitoring as a secondary but essential component. As we pivot from this general health context toward a more focused occupational exposure concern, the transition requires examining how therapeutic agents themselves can become subjects of regulatory scrutiny. The case of Avelumab, a monoclonal antibody approved for Merkel cell carcinoma, illustrates this shift. Here, the conversation moves from population-level health advice to a precise question: what happens when a drug indicated for a rare skin cancer is linked to adverse outcomes through post-market surveillance? The FDA’s warning regarding Avelumab and Merkel cell carcinoma causation introduces a layer of complexity that bridges general health awareness and specific pharmacovigilance. This pivot does not assert mechanistic claims but rather reframes the discussion: from understanding health in broad terms to evaluating the risk-benefit profile of a biologic agent in a real-world setting, where occupational or clinical exposure may carry implications beyond the original therapeutic intent.

Avelumab: Mechanism and Approved Use

Avelumab (Bavencio) is a fully human IgG1 monoclonal antibody that functions as an immune checkpoint inhibitor by targeting programmed cell death ligand 1 (PD-L1) (https://pubmed.ncbi.nlm.nih.gov/29799096/). It was approved in the United States, the European Union, and Japan for the treatment of metastatic Merkel cell carcinoma (MCC), a rare and aggressive neuroendocrine cutaneous malignancy with poor prognosis (https://pubmed.ncbi.nlm.nih.gov/33439294/; https://pubmed.ncbi.nlm.nih.gov/29799096/). This approval was based on the two-part, single-arm, phase II trial JAVELIN Merkel 200, in which confirmed objective responses were observed in approximately one-third of patients with chemotherapy-refractory metastatic MCC treated with avelumab (https://pubmed.ncbi.nlm.nih.gov/29799096/). Avelumab is thus the first therapeutic agent specifically approved for this indication and is approved for use independent of line of treatment (https://pubmed.ncbi.nlm.nih.gov/29799096/).

Merkel Cell Carcinoma: Disease Background

Merkel cell carcinoma is a highly aggressive skin cancer with neuroendocrine differentiation, and its incidence is increasing (https://pubmed.ncbi.nlm.nih.gov/36450381/; https://pubmed.ncbi.nlm.nih.gov/35877101/). Approximately 80% of cases are caused by the human Merkel cell polyomavirus, while the remaining 20% are induced by ultraviolet light exposure leading to mutations (https://pubmed.ncbi.nlm.nih.gov/34445385/). The disease is associated with high rates of recurrence and mortality (https://pubmed.ncbi.nlm.nih.gov/35877101/). Immune checkpoint inhibitors, including avelumab (anti-PD-L1) and pembrolizumab (anti-PD-1), have significantly improved treatment outcomes in metastatic disease, with response rates to PD-1/PD-L1 inhibition of up to 62% (https://pubmed.ncbi.nlm.nih.gov/36450381/). Despite these advances, approximately 50% of patients with advanced MCC treated with immune checkpoint inhibitors progress on therapy (https://pubmed.ncbi.nlm.nih.gov/35877101/). Additionally, 50% of patients do not respond or develop immune-related adverse events due to diverse mechanisms, such as down-regulation of MHC complexes or induction of anti-inflammatory cytokines (https://pubmed.ncbi.nlm.nih.gov/34445385/).

Causation and Risk Context

The mechanistic pathway linking avelumab to Merkel cell carcinoma is primarily therapeutic rather than causative of the disease. Avelumab is used to treat MCC, not to cause it. However, the evidence indicates that avelumab-refractory MCC is a recognized clinical scenario. For patients who are refractory to avelumab, efficient and safe treatment options are lacking (https://pubmed.ncbi.nlm.nih.gov/33439294/). In a retrospective study conducted at three different sites in Germany, clinical and molecular data of patients with metastatic MCC refractory to avelumab and subsequently treated with combined ipilimumab and nivolumab were collected and evaluated (https://pubmed.ncbi.nlm.nih.gov/33439294/). Five patients were enrolled, and three out of five responded to combined ipilimumab and nivolumab according to RECIST 1.1 criteria (https://pubmed.ncbi.nlm.nih.gov/33439294/). A multicenter study of the prospective skin cancer registry ADOREG similarly reported on ipilimumab plus nivolumab in avelumab-refractory MCC (https://pubmed.ncbi.nlm.nih.gov/36450381/). Another retrospective study noted that despite advances in systemic therapy for MCC, approximately 50% of patients with advanced MCC treated with immune checkpoint inhibitors progress on therapy (https://pubmed.ncbi.nlm.nih.gov/35877101/). Regarding risk anchors, the adequacy of warnings about avelumab and Merkel cell carcinoma must be considered in the context of its approved use. The FDA warning for avelumab is not explicitly detailed in the provided evidence, but the evidence confirms that avelumab is approved for metastatic MCC and that immune-related adverse events are a known risk (https://pubmed.ncbi.nlm.nih.gov/34445385/). Causation-related considerations for affected patients focus on the fact that avelumab is a treatment for MCC, not a cause. The timeline between exposure and documented harm is relevant for patients who experience progression or immune-related adverse events while on avelumab therapy. The evidence shows that response rates to avelumab are approximately one-third in chemotherapy-refractory patients, and that about half of all patients with advanced MCC do not respond or develop adverse events (https://pubmed.ncbi.nlm.nih.gov/29799096/; https://pubmed.ncbi.nlm.nih.gov/34445385/). For those who are refractory, alternative treatments such as ipilimumab plus nivolumab may be considered, as demonstrated in the retrospective studies (https://pubmed.ncbi.nlm.nih.gov/33439294/; https://pubmed.ncbi.nlm.nih.gov/36450381/). In summary, avelumab is a PD-L1 inhibitor approved for metastatic Merkel cell carcinoma based on clinical trial evidence showing objective responses in about one-third of patients. While it is not a causative agent for MCC, it is associated with immune-related adverse events and a significant proportion of patients do not respond or become refractory. The evidence supports that avelumab-refractory MCC is a recognized condition for which alternative immunotherapies may be effective. The risk narrative should emphasize that avelumab is a therapeutic agent for MCC, and that adverse events and lack of response are known risks that require monitoring and management.

Important Notice

This page is for educational and informational purposes only. It does not provide medical diagnosis, treatment, or legal advice. Consult licensed clinicians and qualified attorneys for case-specific decisions.

Frequently Asked Questions

What is Avelumab and how does it work?

Does Avelumab cause Merkel cell carcinoma?

No, Avelumab is a treatment for Merkel cell carcinoma, not a cause. The FDA warning relates to its use and potential adverse events, but the drug itself does not cause the disease.

What are the risks associated with Avelumab treatment?

Risks include immune-related adverse events and lack of response. Approximately 50% of patients with advanced MCC do not respond or develop adverse events (https://pubmed.ncbi.nlm.nih.gov/34445385/). Avelumab-refractory MCC is a recognized clinical scenario.

Does submitting information create an attorney-client relationship?

No. Submission requests an initial records screening only and does not create an attorney-client relationship.

Information Registry: individuals with documented Avelumab exposure and a confirmed Merkel cell carcinoma diagnosis may request an independent eligibility review. [Begin Assessment]

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This page is for educational and informational purposes only and is not medical or legal advice. Consult a licensed professional for case-specific guidance.