Cost-effective pricing of long-acting injectable HIV pre-exposure prophylaxis for adolescent girls and young women in South Africa: a model-based analysis

Abstract

Background: Long-acting, injectable cabotegravir (CAB-LA) is more effective than daily oral tenofovir disoproxil fumarate and emtricitabine (TDF-FTC) for HIV pre-exposure prophylaxis (PrEP). We aimed to estimate the maximum price premium: the greatest price markup that society should be willing to accept for CAB-LA compared with TDF-FTC among adolescent girls and young women aged 15-29 years in South Africa.

Methods: Using the Cost-effectiveness of Preventing AIDS Complications model, we simulated adolescent girls and young women (aged 15-29 years) with characteristics similar to the targeted enrolment population of the FastPrEP study in Cape Town, South Africa, to compare daily oral TDF-FTC with bimonthly CAB-LA. The simulation model captured individual and population-level effects from a health-care sector perspective. Model inputs included HIV incidence (off PrEP 3·2 per 100 person-years, TDF-FTC 1·9 per 100 person-years, and CAB-LA 0·2 per 100 person-years), 10-year cumulative HIV transmissions to partners, and PrEP persistence (TDF-FTC 88% and CAB-LA 85% at 2 years) from published data. Annual costs included PrEP programme (TDF-FTC US$28 and CAB-LA $45), PrEP drug (TDF-FTC $40), antiretroviral therapy ($50-890), and HIV-related care ($230-1800). Model-projected outcomes included incident infections among adolescent girls and young women, transmissions, life-years, costs, incremental cost-effectiveness ratios (ICERs), and the maximum price premium of CAB-LA drug at a willingness-to-pay threshold of 50% of the gross domestic product of South Africa per capita ($3500 per life-year). Key parameters were varied in sensitivity analyses.

Findings: Per 10 000 adolescent girls and young women and their partners over 10 years, our model estimates that infections and transmissions would be higher, and life-years would be lower using a TDF-FTC strategy (1980 infections, 450 transmissions, and 88 400 life-years) compared with CAB-LA (1080 infections, 220 transmission, and 88 600 discounted life-years). At 10 years, CAB-LA would be cost-effective with a maximum price premium over TDF-FTC of $38 per year (maximum price of $78 per year) and cost-saving at a drug price of $65 per year. Considering a lifetime horizon, the maximum price premium over TDF-FTC could be seven times higher: $232 per year (maximum price $272 per year).

Interpretation: Our findings suggest that a CAB-LA strategy could reduce transmissions and increase life-years compared with TDF-FTC. The availability of an inexpensive and effective oral alternative medication for adolescent girls and young women in South Africa limits the price that payers should be willing to accept for CAB-LA with a modest markup over TDF-FTC.

Funding: National Institutes of Health and Massachusetts General Hospital Executive Committee on Research.

Figure 1:. Projected 10-year annual component costs for each PrEP strategy

(A) TDF-FTC PrEP strategy. (B) CAB-LA PrEP strategy. Costs are in 2022 US$. Component costs include ART drug prices, HIV care costs, PrEP drug prices, and PrEP programme costs. Results are scaled to 10 000 adolescent girls and young women. ART=antiretroviral therapy. CAB-LA=long-acting, injectable cabotegravir. PrEP=pre-exposure prophylaxis. TDF-FTC=tenofovir disoproxil fumarate and emtricitabine.

Figure 2:. Sensitivity analysis of willingness-to-pay thresholds and varying TDF-FTC and CAB-LA drug prices

Costs are in 2022 US$. The horizontal dotted line represents the annual base-case drug price for TDF-FTC ($40). The vertical dashed line represents the annual base-case drug price for CAB-LA ($78). Adopting an opportunity cost-based threshold of $3000 per life-year (0·43 times GDP per capita) would yield a maximum CAB-LA price of $76 per year. Additional sensitivity analyses on PrEP programme cost are in appendix 1 (p 13). CAB-LA=long-acting, injectable cabotegravir. ICER=incremental cost-effectiveness ratio. TDF-FTC=tenofovir disoproxil fumarate and emtricitabine.

Figure 3:. Maximum price premium of CAB-LA at varying CAB-LA persistence and effectiveness

Costs are in 2022 US$. The maximum price premium based on varying levels of CAB-LA persistence at 2 years and varying levels of CAB-LA effectiveness, as relative improvement over TDF-FTC, are shown. The base-case maximum price premium of a 90% relative improvement in effectiveness of CAB-LA over TDF-FTC with 85% CAB-LA persistence at 2 years is $38. CAB-LA=long-acting, injectable cabotegravir. TDF-FTC=tenofovir disoproxil fumarate and emtricitabine.