ViiV Healthcare, a joint venture of GlaxoSmithKline (NYSE:GSK), Pfizer (NYSE:PFE), and Osaka-based Shionogi, has shown that an injection of cabotegravir every two months is more effective at preventing HIV than Gilead Sciences' (NASDAQ:GILD) Truvada, a once-daily pill which is already approved for use as a pre-exposure prophylaxis (PrEP).

People who took cabotegravir had an HIV incidence rate of 0.38%, compared to a 1.21% rate for the group that took Gilead's Truvada. Put another way, cabotegravir was 69% more effective at preventing the disease than Truvada.

One of the downsides of a medication that comes in the form of a once-daily pill is that people need to remember to take it daily or it becomes substantially less effective. A random blood sampling of people taking Truvada detected one of the components of Truvada at a substantial level in 87% of the samples.

Gloved hands giving an injection in a shoulder

Image source: Getty Images.

On the safety side, 80% of patients reported an injection site reaction with cabotegravir, but only 2% found the issue bad enough that it led them to drop out of the clinical trial.

ViiV plans to use the data to submit cabotegravir for FDA approval as a PrEP treatment, although the company didn't indicate the timing for the submission.

The lack of certainty as regards the timing of the marketing application is likely linked to a December complete response letter -- the Food and Drug Administration's euphemism for a rejection -- for cabotegravir in combination rilpivirine as a treatment for patients infected with HIV. The issue had to do with the chemistry manufacturing and controls section of the marketing application, but ViiV didn't go into detail about the exact issue nor did it speculate about how quickly it might be fixed.