GlaxoSmithKline and Vertex Pharmaceuticals’ HIV drug Lexiva (fosamprenavir) is non-inferior to Abbott Laboratories’ popular rival combination therapy, Kaletra (ritonavir and lopinavir), at least according to preliminary early results of a clinical study comparing the agents’ efficacies.

In the 887-patient study, patients received either Lexiva (sold as Telzir outside the USA) and ritonavir, or Kaletra/ritonavir. In addition, all participants were given daily doses of abacavir and lamivudine - active ingredients in GlaxoSmithKline’s Ziagen and Epivir, respectively, to support antiretroviral therapy. After 48 weeks of treatment, 73% of patients receiving Lexiva exhibited suppression of HIV replication versus 71% in the Kaletra group.

The companies said they undertook the trial because Kaletra is the preferred product for HIV suppression in the Department of Health and Human Services and the International AIDS Society’s treatment guidelines. But as this evaluation seems to suggest that Lexiva is comparable in efficacy to Kaletra, the groups plan to submit final results to health regulators around the world for consideration.