BRISTOL-MYERS' DIDEOXYADENOSINE/DIDEOXYNOSINE PHASE I TRIALS
BRISTOL-MYERS' DIDEOXYADENOSINE/DIDEOXYNOSINE PHASE I TRIALS will begin shortly at the National Cancer Institute, which has been developing the AIDS drugs since 1985. Bristol-Myers has been awarded an exclusive development and marketing contract for the drugs, NCI Director Vincent DeVita, MD, announced at a Feb. 1 meeting of the National Cancer Advisory Board. In May, Health and Human Services announced in the Federal Register that it was considering bids for dideoxyadenosine (DDA) and dideoxyinosine (DDI). Press reports last fall indicated that the agency was close to reaching an agreement with Bristol-Myers, however, no formal announcement has yet been made. The company says that it will issue a statement on the status of the AIDS drugs during the week of February 8-12. HHS' desire to set price controls for the drugs may have been one obstacle to reaching a quick agreement. In the Federal Register announcement last May, HHS asked potential licensees to agree to price controls as a condition of marketing drugs originally developed by the NCI. HHS' became concerned with patient costs of AIDS therapies in response to Burroughs Wellcome's decision to charge $ 8,000 for a year's worth of Retrovir (AZT). DDI is an active metabolite of DDA and conversion occurs within minutes in serum. Therapeutic doses of DDA/DDI in vitro are reportedly less toxic to bone marrow tissue than those of AZT. Bone marrow toxicity has been a major drawback for AZT. NCI Deputy Clinical Director Samuel Broder, MD, speaking last June, said that DDA and DDI "are both profoundly inhibitory. You're looking at about five orders of magnitude inhibition of virus without toxicity to the target cells in this particular system" ("The Pink Sheet" June 8, p. 6). DDA and DDI are chemically similar to dideoxycytidine (DDC), another AIDS drug that also was discovered at NCI and licensed last May to Hoffmann-LaRoche. DDC, however, has serious toxic effects that include anemia and nerve damage, which can result in painful sensations in the extremities. An AZT/DDC Phase I study, in which patients are given the drug on alternate weeks for a six-month period, is ongoing at NCI. "Some of [the patients] are doing well with essentially no toxicity," according to a researcher at the Institute.
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