Dr Nagesh Sirsath, Medical Oncologist, Ruby Hall Clinic
Cancer vaccines are a form of immunotherapy that can help educate the immune system about what cancer cells “look like” so that it can recognise and eliminate them. Vaccines have proven effective in preventing diseases caused by viruses ( measles, polio) and bacteria (e.g., diphtheria, tetanus). Here vaccines work by exposing a person to a weakened or inactivated version of the threat. This enables their immune system to identify these threats according to their specific markers—known as “antigens”—and mount a response against them. These vaccines typically work best in the preventive setting.
In case of cancer, however, the situation is more complicated which has made it more difficult to develop vaccines to prevent or treat cancer. In particular, unlike bacteria and viruses, which appear foreign to our immune system, cancer cells more closely resemble our normal, healthy cells. Furthermore, each individual’s tumor is in some sense unique and has its own distinguishing antigens. Hence at present we have only two approved preventive cancer vaccines including the human papillomavirus (HPV) vaccine approved in 2006, which has dramatically reduced HPV-related cancers and a HBV ( Hepatitis B virus vaccine approved in 1991 which prevents HBV infection and subsequent liver cancer). Approved therapeutic cancer vaccines include Sipeleucel-T used in advanced prostate cancer; BCG used in early stage bladder cancer and T-VEC which is an oncolytic virus-based vaccine used to treat advanced melanoma.
Between 2013 to 2019 there were disappointing results and failures with various cancer vaccines including Stimuvax and Lucanix to treat advanced lung cancer; Rindopepimut to treat the aggressive brain tumor Glioblastoma and MAGE-3 vaccine to treat melanoma and lung cancer. Research is now focusing on personalised vaccines that target patient-specific neoantigens — the proteins that form on cancer cells — as well as vaccines that can treat diverse tumor types. A prime example is a personalised, messenger RNA (mRNA)–based vaccine designed to prevent recurrence of melanoma.
The mRNA-4157 vaccine encodes up to 34 different patient-specific neoantigens. Promising results are also being observed with BNT 116 and Tedopi vaccine in advanced lung cancer treatment; VB10.16 vaccine in cervical cancer and BNT 122 vaccine in preventing pancreatic cancer recurrence. We need more information including larger patient population studies and longer follow-up before these vaccines will actually be utilized in therapeutic setting.
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