- Current solid cancer treatments are based on the location of the tumor, for example breast, lung, or prostate to name a few.
- First ever cancer drug was granted accelerated approval from FDA based on the presence of biomarker specific of genetic abnormality, irrespective of the location of the tumor.
In a first ever instance, the FDA has granted accelerated approval to pembrolizumab
a cancer drug that could benefit patients with DNA abnormalities such MSI-H and dMMR, notwithstanding the location of the tumor in the body.
Pembrolizumab Trial - Methods And Findings
The safety and efficacy of Pembrolizumab
were assessed in patients with solid tumors having MSI-H or dMMR enrolled in one of five single-arm clinical, uncontrolled trials. In some trials, participating patients needed to have MSI-H or dMMR cancers, while in other trials, a subgroup of volunteers was found to be having MSI-H or dMMR cancers by assessing tumor samples after treatment had begun.
- A total of 15 cancer types were found in 149 enrolled patients across these five clinical trials. The most common cancers were colorectal, uterine and other gastrointestinal cancers.
- The trial results of Keytruda was based on the percentage of patients who underwent complete or partial shrinkage of their tumors (overall response rate) and the length or durability of response.
- Of the 149 patients who received Keytruda in the trials, 39.6 percent demonstrated a complete or partial response. For 78 percent of those patients, the effects continued for six months or more.
Some common as well as serious side effects reported during the study have been discussed later.
Pembrolizumab for Unresectable Or Metastatic Solid Tumors With
This novel drug is useful in both adult as well as pediatric solid cancers irrespective of the site in the following situations.
- Tumors considered unresectable
- Cancers progressing in spite of alternate chemotherapy
- Tumors having no satisfactory treatment options
- Tumors that have spread or metastasized to distant sites
FDA had earlier permitted Pembrolizumab (Keytruda) for the treatment of certain patients with metastatic melanoma, metastatic non-small cell lung cancer, refractory classical Hodgkin lymphoma
, recurrent metastatic head and neck cancer, and urothelial carcinoma.
At present, the drug has been tested in patients with unmet clinical needs and for possible benefit in seriously ill patients; t
he FDA has approved accelerated approval to pembrolizumab for cancers with high-microsatellite instability and defective mismatch repair of DNA
‘Cancers with genetic abnormalities such as microsatellite instability-high (MSI-H) and mismatch repair deficient (dMMR) can be treated by pembrolizumab, irrespective of tumor site.’
Tumors with these biomarkers are most commonly found in colorectal, endometrial and gastrointestinal cancers
, but also less commonly appear in cancers arising in the breast, prostate, bladder, thyroid gland and other places. Approximately 5 percent of patients with metastatic colorectal cancer have MSI-H or dMMR tumors.
"This is an important first for the cancer community," said Richard Pazdur, M.D., acting director of the Office of Hematology and Oncology Products in the FDA's Center for Drug Evaluation and Research and director of the FDA's Oncology Center of Excellence. "Until now, the FDA has approved cancer treatments based on where in the body the cancer started—for example, lung or breast cancers. We have now approved a drug based on a tumor's biomarker without regard to the tumor's original location."
Mechanism of Action of Pembrolizumab
Pembrolizumab is a monoclonal antibody that acts by targeting the PD-1/PD-L1
(proteins found on the body's immune cells and some cancer cells) cellular pathway
. By blocking this pathway
, Pembrolizumab helps the body's immune system to fight the cancer cells.
Safety Factor of Pembrolizumab
Common side effects of Pembrolizumab include tiredness, itchy skin (pruritus), rash, fever (pyrexia), nausea, diarrhea, reduced appetite, cough, difficulty in breathing (dyspnea) and musculoskeletal pain.
Serious toxicity or immune-mediated side effects, include inflammation of organs such as lungs (pneumonitis), colon (colitis),) kidneys (nephritis), liver (hepatitis), endocrine glands (endocrinopathies).
Complications including death related to allogeneic hematopoietic stem cell transplantation
have been reported after using Pembrolizumab.
Pembrolizumab is contraindicated in patients who develop severe and life-threatening reactions to infusions and during pregnancy, as the drug may harm the fetus. The safety and efficacy of Pembrolizumab in children with MSI-H central nervous system cancers have not been established. References:
- FDA approves first cancer treatment for any solid tumor with a specific genetic feature - (https://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm560167.htm)