BACKGROUND: Worldwide, 1.5 million people acquired HIV in 2021. Cabotegravir is the most effective drug to prevent HIV acquisition, with estimated efficacy of 90-95%, superior to oral tenofovir/emtricitabine(TDF/FTC). TDF/FTC is available as generic PrEP in most countries, costing $48/year in LMICs. CAB-LA costs $22,200/year in US, $9000 in the UK. The ViiV-MPP licence permits generic companies to sell CAB-LA at low prices, estimated $250/year. However, the ViiV-MPP agreement excludes many middle-income countries, such as Brazil. CHAI estimated costs of production of $34-$63/year(median $50).
METHODS: We modelled the effects of 4 strategies for PrEP in Brazil: 1.No PrEP used 2.TDF/FTC generic used for PrEP, costing $48/year. 3.CAB-LA used, with a high price, outside the ViiV-MPP license:$3500/year, (68% below UK price), or $250/year (target price). 4.CAB-LA used at CHAI target price $50/year. TDF/FTC and CAB-LA were assumed to lower HIV acquisition risks by 70% and 94% respectively, versus no PrEP. We assumed a target population of 125,000 people at high risk of HIV acquisition (incidence 6%), treated in Brazil with annual budget of $6million.
RESULTS: Using TDF/FTC costing $48/year, the $6 million Brazilian PrEP budget could treat all 125,000 people, lowering annual HIV acquisition from 8750 to 2525/year. By contrast, use of CAB-LA for $3500/year covers 1714 people; the remaining 123,285 people receive no PrEP. Even at target prices of $250/year, overall HIV acquisition rates are still higher. The CHAI cost price of $50/year would provide for 120,000 people, lowering HIV acquisition to 854/year. CAB-LA needed to cost less than $80/year to lead to fewer HIV acquisitions than TDF/FTC.
CONCLUSIONS: When demand for PrEP is high and budgets limited, CAB-LA will only lower overall HIV acquisition rates if costing <$80/year. If prices are higher, limited people can be given CAB-LA: then, mass use of TDF/FTC for $48/year allows increased coverage, lowering overall HIV acquisition rates. Compulsory licensing may be required to lower CAB-LA prices in countries outside the ViiV-MPP voluntary license.

Budget	Cost of PrEP	Number given PrEP	HIV acquisitions
Current PrEP budget-$6million
No PrEP	$0	0	8750
TDF/FTC	$48	125,000	2250
CAB-LA base case	$3500	1714	8637
CAB-LA target price	$250	24,000	6632
CAB-LA cost price	$50	120,000	732