Even though a drug is sometimes developed with a certain condition in mind, it can be used to effectively treat or manage alternate conditions. For example, pembrolizumab (KEYTRUDA) is often prescribed for patients with melanoma, Merkel cell carcinoma (MCC), breast or cervical cancer, stomach cancer, or urothelial carcinoma (among others). According to OncLive, the U.S. Food and Drug Administration (FDA) recently expanded the label for pembrolizumab to include locally advanced cutaneous squamous cell carcinoma (cSCC) which cannot be treated or cured using surgery or radiation.
Pembrolizumab
According to the National Cancer Institute (NCI), pembrolizumab is:
A humanized monoclonal immunoglobulin (Ig) G4 antibody directed against human cell surface receptor PD-1 (programmed death-1 or programmed cell death-1) with potential immune checkpoint inhibitory and antineoplastic activities. Upon administration, pembrolizumab binds to PD-1, an inhibitory signaling receptor expressed on the surface of activated T cells, and blocks the binding to and activation of PD-1 by its ligands, which results in the activation of T-cell-mediated immune responses against tumor cells.
In short, pembrolizumab is an immunotherapy which works with the immune system to fight cancer. The recent label expansion to include pembrolizumab as a monotherapy for cSCC hinged upon data from the Phase 2 KEYNOTE-629 clinical trial. Altogether, 213 patients enrolled. Of these, 54 patients had locally advanced cSCC, while the remaining patients had advanced recurrent or metastatic cSCC. During the trial, patients received 200mg pembrolizumab every 3 weeks until patients either reached toxicity, were treated for 24 months, or had their condition progress.
Findings from the study include:
- Altogether, pembrolizumab achieved a 50% overall response rate within the locally advanced group. Of this, 17% of patients achieved complete response, with the remaining 33% reaching partial response.
- In 81% of those who achieved a response, the response duration lasted for over 6 months. In 37% of patients, the response was sustained for a year or longer. Alternately, in patients with recurrent or metastatic cSCC, the median response duration was 6.9 months.
- While pembrolizumab was relatively safe and well-tolerated, some moderate-to-severe adverse reactions did occur. These include lowered sodium levels and lymphopenia (low lymphocyte levels).
Cutaneous Squamous Cell Carcinoma (cSCC)
Cutaneous squamous cell carcinoma (cSCC), or squamous cell carcinoma of the skin, is the second most common skin cancer. It affects the squamous cells in the middle and outer layers of skin. Although cSCC often affects areas with high sun exposure, this cancer can appear all over the body. With early diagnosis and treatment, cSCC can be treated and cured. Risk factors for cSCC include having fair skin, being immunocompromised, using tanning beds or having excessive sun exposure, having a history of sunburn or skin cancer, or having rare genetic disorders. Symptoms of cSCC include:
- New sores appearing on old scores
- Flat or open sores
- Red skin nodules
- Scaly patches on the lips
- Inner mouth sores
- Thick or wart-like skin
- Skin crusting, itching, or bleeding
