Estimating Probabilities of Success of Clinical Trials for Vaccines and Other Anti-Infective Therapeutics

Chi Heem Wong; Kien Wei Siah; Andrew W Lo

As technology continues to advance, one expects that the human species will be better able to cope with these diseases. The fact remains, however, that we still do not have effective treatments or vaccines for many infectious diseases. While the discovery of antibiotics has reduced the mortality rate of bacterial infection, and the development of the smallpox vaccine has led to the eradication of the devastating disease (World Health Organization, 1980) , other infectious diseases, such as Acquired Immunodeficiency Syndrome (AIDS) and A drug development program is the clinical investigation of the use of a drug for a disease, typically consisting of sequential clinical trials, separated into phases. We make the assumption that each program must transition from phase 1 to phase 2 to phase 3 to approval. We say that a drug development program has reached phase i if it is observed, or can be inferred, that there is at least one trial in phase i. The probability of a drug development program transitioning from phase i to phase j (PoSij) can be computed using the simple ratio Nj/Ni, where Ni is the number of drug development programs initiated at phase i (where i = 1, 2, or 3) with known outcomes between phase i and phase j (where j = 2, 3, or "A" which denotes regulatory approval), and Nj is the number of drug development programs among the former that made it to phase j.