In Cambodia, the current national guidelines recommend ART for all patients regardless of CD4 cell
count with a test and treat approach. The recommended first-line regimen in Cambodia includes
tenofovir (TDF)/lamivudine (3TC)/dolutegravir (DTG), whereas the second-line regimen in case of
failure of DTG-based first-line regimen includes zidovudine (AZT)/3TC/atazanavir (ATV)/r. For patients
already treated with NNRTI-based first-line regimen, the current guidelines recommend AZT/3TC/DTG
for those failing NNRTI-based regimen. The last treatment cascade estimates by UNAIDS revealed that
among the 74,000-estimated number of PLHIV in Cambodia in 2021, 62,636 (84%) were aware of their
status, 62,561 (84%) were on ART, and 60,976 (82%) were virologically suppressed. During the course
of ART, HIV VL monitoring is recommended at 6 and 12 months after the initiation of treatment, and
then yearly. For patients with virological failure (VF), an adherence boosting of 3 months is required
before repeating HIV VL testing. If HIV VL remains detectable, switching to ARV second-line regimen is
recommended. There is still limited access to genotypic drug resistance testing. Currently, genotypic
resistance testing is performed at Pasteur Institute of Cambodia (IPC), mainly for patients who have
failed PI-based second-line treatment, which represents a very limited number of patients.

HIV Pre-treatment Drug Resistance (PDR) surveillance was not implemented since decade and pretherapy genotypic resistance testing is not recommended. However, increasing trend of PDR have
been reported in neighbouring countries. As Cambodia scale up the use of DTG-based first-line ART, it
remains important to conduct periodic PDR surveys to document any signals of increases in pretreatment resistance to integrase strand-transfer inhibitors that may affect population-level treatment
outcomes. In the same time, routine surveillance of PDR to tenofovir disoproxil fumarate (TDF) and
emtricitabine (FTC) or lamivudine (3TC) must be implemented as PrEP programmes scale up. DTGbased first-line and second-line regimen has been widely implemented since 2019. By Q3 2022, there
were 39,242 PLHIV had started DTG first-line regimen and 25 patients were on the second-line
regimen. However, data of acquired drug resistance (ADR) in patients failing DTG-based regimen are
unavailable. Surveillance for NRTI and DTG-resistant virus among people for whom DTG-containing
regimens are failing will be required.
In addition to the individual need for access to resistance genotyping for PLHIV who have failed
treatment, WHO recommends regular monitoring of the prevalence of resistance in order to better
adapt management programmes to the population. This WHO strategy on HIV drug resistance was
updated in 2021 and specifically recommends: 1) a national action plan on HIV drug resistance; 2)
monitoring of early warning indicators of HIV drug resistance; and 3) surveillance of HIV drug
resistance.
In response to these recommendations, the implementation of an HIV ARV resistance survey was
planned in the last Global Fund grant. However, in the absence of specific recommendations for ARV
resistance surveillance in the national strategic plan, as well as limited access to resistance genotyping
testing, this activity has not been carried out.
It is essential to build national ownership of ARV resistance prevention, surveillance and management.
It is necessary to develop operational recommendations for biological and clinical management that
are feasible and adapted to the context, combined with a training programme for actors on the
challenges of ARV resistance.
Finally, the lack of local capacity to screen for HIV drug resistance is a challenge. Genotypic resistance
testing is currently carried out in the IPC biology laboratory, but alternative options need to be
explored. The WHO HIVResNet network, which includes two laboratories in Bangkok and one in Ho Chi
Minh City, is developing a training programme and may be an option to increase laboratory set-up
within NCHADS. The use of DBS (blotting paper) could also be an interesting alternative to perform
ARV resistance testing in decentralised areas where access to viral load is already a problem.
This technical assistance request aims at filling this gap by defining and developing a national action
plan for HIV drug resistance surveillance.