A new treatment for osteoporosis that can be given just once every three months has been approved by the US Food and Drug Administration.

Boniva for injection (ibandronate sodium), developed by GlaxoSmithKline and Roche, is aimed at people who find it hard to adhere to treatment with the current oral formulations of ibandronate and other drugs in the bisphosphonate class, which are the most frequently prescribed drugs for osteoporosis.

Studies suggest that despite the effectiveness of bisphosphonates, less than half of patients continue on treatment long-term because of side effects, particularly irritation of the upper gastrointestinal tract, as well as complex dosing instructions such as a requirement to sit upright for 30 to 60 minutes after dosing.

This suggests there could be a ready market for an injectable version that bypasses these problems, according to analysts, who have predicted that the new Boniva formulation could achieve sales of around $1 billion dollars at its peak. It is the only injectable bisphosphonate drug on the market.

Roche and GSK have worked hard to develop more patient-friendly formulations of Boniva (sold as Bonviva in Europe) since launching it as a once-daily oral product in 2003. This version has seen modest sales growth, as it was competing with once-weekly products including market leader Merck & Co’s Fosamax (alendronate), which makes more than $3 billion a year.

In comparison, Boniva sales were $13 million for GSK and $28 million for Roche in the first nine months of 2005. But last year Roche and GSK launched a once-monthly formulation last April which should lend some momentum to the franchise as the injectable formulation starts to build market share.

The competitive nature of the market for osteoporosis drugs was illustrated last week when Procter & Gamble Pharmaceuticals and Sanofi-Aventis, which make a rival drug called Actonel (risedronate sodium), asked a court to put an end to what they claim is false advertising for Boniva.