British drugmaker GSK has struck a deal to allow low-cost generic versions of its long-acting HIV preventive medicine to be used in the developing world, including sub-Saharan Africa where the virus remains a leading cause of death.

Each year, roughly 1.5 million new cases of HIV are recorded globally, most of which occur in resource-limited countries, and disproportionately impact women and adolescent girls.

The deal involves GSK issuing a voluntary licence - so the intellectual property does not get in the way - to the United Nations-backed healthcare organisation, the Medicines Patent Pool (MPP).

Following that, the MPP offers generic manufacturers the opportunity to apply to make copycat versions of the injected drug, cabotegravir, for the 90 countries that represented 70% of all new HIV cases in 2020.

Pre-exposure prophylaxis (PrEP) is an effective way for an at-risk HIV-negative person to reduce the risk of infection. But until recently, PrEP was only available in pill form, taken daily, or, in some cases, before and after sex.

This is partly why it is being used by a fraction of people that are eligible globally, and there is particularly poor uptake in poorer countries.

GSK's product is the first non-pill option, offering up to two months of protection against infection via a single intramuscular injection, and studies show it even outperforms oral pill efficacy.

It secured U.S. approval late last year, and on Thursday the World Health Organization also endorsed its use to help accelerate efforts to make injectible cabotegravir a part of the arsenal of global HIV prevention tools.

Campaigners have called for the drug to be available as quickly, widely and cheaply as possible, fearing a repeat of the 1990s and early 2000s, when poor countries were priced out of HIV therapy for years.

For that, injectable cabotegravir needs to be cleared for use by regulators in each country. Generic manufacturers also need to meet required MPP and regulatory standards.

Given these factors, the first generics will potentially only become available in 2026, said Deborah Waterhouse, chief of the GSK's HIV division, ViiV Healthcare.

In the interim, GSK is working on providing governments the regimen free of charge to run studies to understand the best way to roll the product out.

A six-dose regimen of injectable cabotegravir is sold for $22,000 per year in the United States - the same as the U.S. price of Gilead's oral PrEP regimen, Descovy, Waterhouse said.

After those studies are done, an annual course of injectable cabotegravir will cost governments "hundreds of dollars" per person, instead of thousands, said Waterhouse.

That price encompasses ingredient, labour and electricity costs, she added, "there's no profit made whatsoever."

With regulatory approvals and implementation studies yet to read out, it will likely take up to two years before a substantial order is placed, she said.

If the 'not-for-profit' price is hundreds of dollars a year, it's unlikely governments from poorer countries and health funding bodies like the Global Fund can afford it, said UNAIDS deputy executive director Matthew Kavanagh.

But if it is under $100 and closer to $60, then it could be a game-changer, he added.