Iffy showing in trials prompts rifalazil bailout
Company backs second drug instead
PathoGenesis Corp., a Seattle-based pharmaceutical firm, recently announced its decision to cancel plans for further trials of rifalazil (PA-1648), an agent that originally had seemed to show promise as a new anti-TB drug.
Rifalazil didn’t perform as well as had been hoped in Phase II trials, which showed what the company terms "inconclusive indication of efficacy," a spokesman for PathoGenesis says. Moving ahead to a larger-scale trial might have cleared up the ambiguity, but the decision was made instead to back a more certain winner the company also has under development.
The surer bet may be Tobramycin, company executives decided. Because it is an aerosolized antibiotic that delivers medication more rapidly to the lungs than oral antibiotics, researchers hope Tobramycin eventually may be useful in shortening the duration of anti-TB therapy. The drug recently completed Phase II trials that examined its usefulness in the treatment of another lung condition, bronchiectasis; it is still undergoing Phase II trials designed to test its usefulness against TB.
Rifalazil, a new member in the family of rifamycins, had sparked the interest of researchers and outside observers because of its unusually long half-life, which suggests the agent could be administered as infrequently as once a week or even once every two weeks. Phase I trials raised questions about toxicity, however, prompting a scale-back in dosage in the successive trial phase.
PathoGenesis, a small newcomer firm based outside Seattle, specializes in the development of new agents for use against chronic diseases, and lung diseases in particular.
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