New drug development during and after a period of regulatory change: clinical research activity of major United States pharmaceutical firms, 1958 to 1979.

The 1962 drug amendments fundamentally changed the way in which U.S. pharmaceutical firms could test new drugs in man and receive New Drug Application (NDA) approval. Although it is well known that the amendments and associated events caused a profound decline in the annual number of new drugs receiving NDA approval, the amendments' effects on clinical research into new chemical entities (NCEs) have not been investigated because data were unavailable. To study this we requested drug development information dating back to 1958 from most major United States-owned pharmaceutical firms and obtained complete responses from nine. The results showed that the introduction rate of NCEs into human testing dropped sharply in the early 1960s and declined substantially thereafter. The number of NCEs entering human testing fell from a mean of 89 a year in 1958-1962, to 35 a year in 1963-1972 (a reduction of 61%), and to 17 a year in the last 5 years of the survey, 1975-1979--an overall reduction of 81%. The number of NDA approvals received by these firms fell sharply by 49% in the early 1960s and more slowly for 10 years thereafter, from the mid-1960s to the mid-1970s. In the case of self-originated NCEs, the size of this later fall was 71%. Causes of these changes in NCE flow include the amendments and the events that prompted them; changes in scientific philosophy, standards, and state of the art; and economic factors.