Antares Pharma Inc said its once-weekly testosterone injection met the main goal in an ongoing late-stage study in testosterone-deficient adult males.
The U.S. Food and Drug Administration asked Antares last month for additional safety data on the drug, to be sold as QuickShot Testosterone, after a patient developed hives in a separate mid-stage trial.
The current late-stage study is testing the drug, known chemically as testosterone enanthate, in 150 patients whose testosterone blood levels are less than 300 nanograms per deciliter.
QuickShot Testosterone, or QST, is the only self-administered subcutaneous treatment in late-stage development, giving it an edge over existing injectables that must be administered directly into the muscle by a doctor.
Patients in the QST late-stage study will remain on the product and be monitored for an additional 40 weeks, but so far there have been no complaints of hives, Antares said, adding that the collection of safety data was continuing.
The FDA has become increasingly vigilant about testosterone products after it was revealed late last year that more than a fifth of males prescribed these drugs did not test their testosterone levels before or during treatment.
Antares, whose shares were up 16.3 percent at $2.92 in premarket trading on Wednesday, said it had already factored in many of the agency's January recommendations in the late-stage study.
The company said it could need 70 more subjects exposed to QST for six months to meet the FDA's recommendations, based on the number of subjects in previous studies and in the current late-stage study.
Prescriptions for low testosterone, or "Low T", have soared over the past decade as middle-aged men face declining testosterone levels.
Up to Tuesday's close, Antares' stock has dipped about 4 percent since Jan. 13, when the FDA asked for additional safety data on the drug.
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