Antares Pharma, Inc. (NASDAQ: ATRS) today announced that the Annals of the Rheumatic Diseases has published results from an open-label, head-to-head randomized, crossover study comparing the relative bioavailability, safety and tolerability of OTREXUP to oral methotrexate (MTX) in adult patients with rheumatoid arthritis (RA).
In this multicenter, three-way crossover study, patients greater than or equal to 18 years old with adult RA undergoing treatment with MTX for three months or more were assigned to receive one of four dose levels of OTREXUP, 10 mg, 15 mg, 20 mg, and 25 mg weekly in a random sequence of three treatments: oral, subcutaneous into the abdomen and subcutaneous into the thigh. For 24 hours after the administration of each treatment, blood samples were collected to measure drug levels and injection sites were assessed. Forty-seven patients completed the study and the results showed that the systemic availability of methotrexate following oral dosing plateaus at 15 mg and greater. Following administration of OTREXUP, the systemic availability increased proportionally at every dose, which extended the range of exposure compared to patients receiving oral therapy. No unexpected adverse events were noted for either formulation in this short term study and higher systemic MTX exposure was not associated with increases in adverse events.
“The study results show for the first time that plasma levels of oral dosed MTX are no greater for 20 mg or 25 mg doses than for 15 mg doses,” said Michael H. Schiff, M.D., Clinical Professor of Medicine in the Rheumatology Division at the University of Colorado School Of Medicine in Denver. “If a patient fails to respond to 15 mg of MTX orally, it may be more effective to switch to a subcutaneous regimen rather than continue to raise the oral dose. These findings may have implications on future prescribing habits of specialists.”