How a personalised cancer vaccine could cut risk of death by half

Here’s how the vaccine would work, what the Merck-Moderna study found, and its significance for cancer treatment in India.

How does intismeran work?

The therapy is designed by identifying the mutations in a patient’s tumour sample: together, these identifying proteins — called neoantigens — act like the fingerprint of their cancer. Neoantigens are essentially proteins that are found only on the cancerous cells, which the body’s immune system can be trained to recognise. These neoantigens vary from person to person, meaning they become an identifier for their cancer but also necessitating personalised vaccines.

The vaccine consists of synthetically developed mRNA that encodes for these proteins. mRNA, or messenger RNA, is a single-stranded molecule that carries genetic instructions from DNA in the cell nucleus. By telling the cell which proteins to make, it acts as a molecular blueprint. Each treatment consists of mRNA coding for 34 such neoantigens. Once administered, the body generates these proteins and presents them to the immune system.

The idea behind the therapy is the same as any other vaccine: teach the immune system to recognise the cancer’s fingerprint so that it can mount an effective response whenever it spots these mutated cells.

“Just as a vaccine for an infectious disease contains the antigen from a pathogen —  the proteins or lipids that trains the body’s immune system to recognise and fight off the pathogen — therapies such as this contain cancer neoantigens. While people have been working on this for a decade or so, this is the first clinical breakthrough,” Dr Gaurav Kharya, haematologist and co-founder of the startup developing blood cancer treatment Cellogen, told The Indian Express.

“The benefit is that this fingerprint of the cancer goes into the immune system’s memory. So, if the cancer comes back, the body’s immune system can immediately recognise it and mount a response, prolonging recurrence-free survival,” he added.

What did the study find? 

The study found that when the vaccine was given with the popular immunotherapy drug Keytruda, the risk of death owing to recurrence of skin cancer went down by 49% — and the risk of death owing to its spreading went down by 59%.

The results are in comparison to only Keytruda being used, which in itself has over the years shown to be much more effective in treatment of certain cancers as compared to traditional chemotherapy.

The most common side effects noted in the study were fatigue, injection site pain, and chills. 

Is this significant for India?

When it comes to the current treatment, the impact would be limited, say oncologists. This is mainly because of two reasons: 

One, the current trial result is only meant for skin cancer, or melanoma. “While melanoma is one of the most common types of cancer in the caucasian population, it is not commonly seen among Indians. Melanoma is, in fact, rare here,” Dr Abhishek Shankar, oncologist at AIIMS-New Delhi, told The Indian Express. Globocan — short for Global Cancer Observatory, an online platform that maintains global cancer statistics — shows that melanoma accounts for only 0.26% of all cancer cases in India and 0.17% of deaths.

Two, is the cost factor. While Keytruda has been shown to be effective in the treatment of several types of cancers, most patients in India are unable to afford it, even with patient assistance programmes.

A real-world study from Tata Memorial Hospital had shown that only 1.6% of the patients who need such immunotherapy are able to access them. “Cost is a very significant factor in India. How can they afford the combination therapy when they cannot afford the immunotherapy itself?” said Shankar.