By Ludwig Burger

(Reuters) – GlaxoSmithKline said an injection every other month of its cabotegravir drug was shown to avert an HIV infection more effectively than Gilead’s daily Truvada pill, potentially giving its ViiV unit a foothold in HIV prevention.

The drug trial involving men who have sex with men was stopped early by an independent monitoring board after cabotegravir was found to be 69% more effective than the current standard of care, Truvada, the British drugmaker said on Monday.

But the market segment GSK is eyeing is about to become more competitive as cheaper generic versions of Truvada are expected to be launched in the United States in September, as the patent expires.

Gilead, for its part, hopes that Truvada users will opt against the cheaper copies and switch to its new daily pill Descovy, approved in October 2019 after it was shown to be less toxic to the kidneys and bones.

Truvada generated $2.8 billion in sales last year, both from treatment and preventing an HIV infection.

Kimberly Smith, ViiV’s head of research, said a long-acting injection was a better route of administer because users have shown to struggle with a strict routine of daily pills, heightening the infection risk.

“Individuals have to show up every eight weeks in the clinic for the injection but in-between there is not a need to take a pill daily, so you really change the equation for adherence with a long acting (drug),” Smith said.

GSK, which is trailing Gilead in the HIV treatment market, will speak to drug regulators about a possible approval of cabotegravir based on the prevention trial, a spokesman said.

Its shares were up 1.25% at 1120 GMT, outperforming a 0.8% gain in the STOXX Europe 600 Health Care

Prevention “has turned into a multi-billion opportunity for Gilead but we think consensus estimates include little or nothing for GSK in this market,” UBS analysts said in a research note.

GSK has won approval in Canada for cabotegravir as one of two key ingredients in long-acting HIV treatment combination Cabenuva, whereas in the United States, the company has run into delays seeking the go-ahead for Cabenuva.

An initial readout from the trial, which started in late 2016, was previously not expected before next year.

A similar trial to test the cabotegravir injection to prevent HIV in women, is still ongoing.

Pfizer and Shionogi & Co Ltd hold small stakes in GSK’s HIV-focused ViiV Healthcare division.

(Reporting by Ludwig Burger, editing by Louise Heavens)