The choice of the primary endpoint in a trial conducted to obtain marketing authorisation is a strategic decision for a pharmaceutical company. It is simpler and cheaper to choose an endpoint that occurs frequently, is sensitive to small changes and is easy to measure, rather than a relevant endpoint that occurs infrequently or is difficult to reproduce or to quantify.

The primary endpoint chosen for the evaluation of capsules of peanut protein as desensitisation therapy for patients with peanut allergy was a standardised tolerance test, conducted in hospital (see “Peanut protein (Palforzia°) for oral desensitisation” > HERE). The evaluation data obtained under these specific conditions showed a reduction in the incidence and severity of allergic reactions elicited by this test. But analysis of the adverse events showed that patients who received these capsules experienced more allergic reactions, including severe reactions, in everyday life than patients who received the placebo.

A few months ago, we wrote about the evaluation of fenfluramine, an amphetamine authorised for use in children with a serious form of epilepsy (Fintepla°), see "Dravet syndrome: fenfluramine (Fintepla°) for children is unacceptable" (> HERE). The endpoint used to evaluate its efficacy was the frequency of convulsive seizures, which the drug markedly reduced. But analysis of adverse events showed a higher incidence of convulsive status epilepticus, which consists of prolonged convulsive seizures that can leave serious neurological sequelae.

Certain endpoints that are easy to study within a short time frame can mask outcomes that really matter to patients. By choosing them, pharmaceutical companies can obtain marketing authorisation more easily and generate the sales and profits they want. It is certainly not a strategy that ensures high-quality treatments that improve patient care.

©Prescrire 1 June 2022

Source: "Strategic choices" Prescrire International 2022; 31 (238): 154. Subscribers only

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