Unlike chemotherapy, which directly damages cancer cells, pembrolizumab doesn't have the same kind of immediate toxicity. Side effects are generally related to the immune system becoming overactive, leading to conditions like colitis, pneumonitis, or thyroid issues. These are called 'immune-related adverse events'.

The high cost is a massive barrier. In India, a single vial can cost over ₹1.5 lakh, and a patient might need multiple vials. Even with patient assistance programs like Merck's 'Kiran', which offers free vials after initial purchase, the upfront cost can be around ₹10 lakh. This 'financial toxicity' puts it out of reach for most.

The drug's patent is set to expire around 2028, after which generic versions could become available, potentially lowering costs significantly. However, Merck has filed numerous follow-on patents that could extend market exclusivity for years.

A significant issue highlighted in recent investigations is the rise of counterfeit Keytruda. Because the drug is so expensive and in high demand, fake versions are being sold, often in genuine-looking packaging. This poses a grave risk to patients, as they may receive ineffective or even harmful substances.

The WHO has included pembrolizumab on its list of essential medicines, recognizing its importance. However, the high price means many low and middle-income countries struggle to afford it, leading to discussions about dose optimization and procurement strategies.

For UPSC, examiners test understanding of immunotherapy as a concept, its mechanism (PD-1/PD-L1), its advantages over chemotherapy (targeted action, potential for durable response), and critically, the socio-economic implications: high cost, access issues in India, and the ethical dilemmas faced by doctors and patients. The recent investigations into pricing, counterfeit drugs, and dosing debates are prime UPSC material.

A common mistake students make is confusing immunotherapy with chemotherapy. They are fundamentally different. Immunotherapy empowers the body's own system, while chemotherapy directly attacks cells. Also, students often overlook the massive access and affordability issues, which are crucial for Mains answers.

The drug is approved for specific cancer types. Using it for other cancers ('off-label use') without strong clinical evidence is a concern for manufacturers and regulators, though some oncologists advocate for it in specific, difficult-to-treat cases when standard options fail.

The regulatory approval process in India can lag behind the US FDA. This gap means that even if a drug is approved elsewhere for a new cancer type, Indian patients might not be able to access it through assistance programs until India's own drug regulator, the CDSCO, approves it for that specific indication.

Unlike chemotherapy, which directly damages cancer cells, pembrolizumab doesn't have the same kind of immediate toxicity. Side effects are generally related to the immune system becoming overactive, leading to conditions like colitis, pneumonitis, or thyroid issues. These are called 'immune-related adverse events'.

The high cost is a massive barrier. In India, a single vial can cost over ₹1.5 lakh, and a patient might need multiple vials. Even with patient assistance programs like Merck's 'Kiran', which offers free vials after initial purchase, the upfront cost can be around ₹10 lakh. This 'financial toxicity' puts it out of reach for most.

The drug's patent is set to expire around 2028, after which generic versions could become available, potentially lowering costs significantly. However, Merck has filed numerous follow-on patents that could extend market exclusivity for years.

A significant issue highlighted in recent investigations is the rise of counterfeit Keytruda. Because the drug is so expensive and in high demand, fake versions are being sold, often in genuine-looking packaging. This poses a grave risk to patients, as they may receive ineffective or even harmful substances.

The WHO has included pembrolizumab on its list of essential medicines, recognizing its importance. However, the high price means many low and middle-income countries struggle to afford it, leading to discussions about dose optimization and procurement strategies.

For UPSC, examiners test understanding of immunotherapy as a concept, its mechanism (PD-1/PD-L1), its advantages over chemotherapy (targeted action, potential for durable response), and critically, the socio-economic implications: high cost, access issues in India, and the ethical dilemmas faced by doctors and patients. The recent investigations into pricing, counterfeit drugs, and dosing debates are prime UPSC material.

A common mistake students make is confusing immunotherapy with chemotherapy. They are fundamentally different. Immunotherapy empowers the body's own system, while chemotherapy directly attacks cells. Also, students often overlook the massive access and affordability issues, which are crucial for Mains answers.

The drug is approved for specific cancer types. Using it for other cancers ('off-label use') without strong clinical evidence is a concern for manufacturers and regulators, though some oncologists advocate for it in specific, difficult-to-treat cases when standard options fail.

The regulatory approval process in India can lag behind the US FDA. This gap means that even if a drug is approved elsewhere for a new cancer type, Indian patients might not be able to access it through assistance programs until India's own drug regulator, the CDSCO, approves it for that specific indication.