What is dostarlimab? Experimental cancer drug causes tumor to disappear from ALL trial participants

What is dostarlimab? Experimental cancer drug causes tumor to disappear from ALL trial participants
(L-R) Sascha Roth, Dr Luis Diaz, Imtiaz Hussain, Dr Andrea Cercek, Avery Holmes and Nisha Varughese were involved in the trial of rectal cancer drug (Photo by Memorial Sloan Kettering Cancer Center)

In a recent experiment, a drug appeared to clear every patient of rectal cancer with minimal side effects in a study done at Memorial Sloan Kettering Cancer Center (MSKCC). “I believe this is the first time this has happened in the history of cancer,” said Dr Luis Diaz of MSKCC and author of the paper published in the New England Journal of Medicine.

The drug, called dostarlimab, was given to 14 people with a specific type of rectal cancer every three weeks for six months. After the course of treatment, cancer was untraceable on physical exam, endoscopy, PET, and MRI scan for every person, the researchers from MSKCC said in a presentation at the annual meeting of the American Society of Clinical Oncology on Sunday, June 5.


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What is dostarlimab?

The drug, dostarlimab, works by helping the immune system identify and destroy cancer cells. The drug, which is branded as Jemperli, is already used for patients with endometrial cancer. As per WebMD, monoclonal antibodies like dostarlimab are laboratory-made antibodies designed to fight specific illnesses. It got popular during the two years as a variety of monoclonal antibodies came out to treat Covid-19. The drug is specifically designed to block a particular protein involved in cancer cells called PD-1. Like, in the Memorial Sloan Kettering trial with rectal cancer, all of the patients' tumors also had a feature known as mismatch repair deficiency in which cells have mutations that keep them from fixing mistakes when DNA is copied.

The participants of the dostarlimab trial didn't require any other form of treatment for up to one year and there were no major side effects to impact day-to-day activities. One of the patients and the first patient in a clinical trial involving immunotherapy, Sascha Roth said, as stated on the official website, "I was so happy when Dr Cercek told me that the latest tests showed no evidence of cancer."

Dr Andrea Cercek, an oncologist at MSKCC and a study co-author, said there were a lot of happy tears from the trial participants when they found out no further treatment was necessary. Cercek also mentioned in a press release that the implications of standard cancer treatment on people's quality of life were substantial, especially in those where standard treatment would impact childbearing potential.

As reported by Stat, the study's approach is built on previous work by Diaz, who pioneered the development of Keytruda, to treat patients with mismatch repair deficiency. In May 2017, the Food and Drug Administration granted approval to Keytruda as a treatment for patients whose tumors had spread beyond their original location.

Unclear if drug is safe enough

Hanna K Sanoff, an oncologist at the Lineberger Comprehensive Cancer Center at the University of North Carolina, wrote in a New England Journal editorial that it was a compelling study. However, she cautioned that the outcome was an imperfect proxy for long-term cancer control. She said, "Cancer regrowth occurs in 20 to 30% of such patients when the cancer is managed nonoperatively. It is unclear if it would be safe to roll out the drug on a large scale. The study was also too small to show rarer side effects."

"These results are cause for great optimism, but such an approach cannot yet supplant our current curative treatment approach," she further added.

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