New contraindication against using darunavir/cobicistat during pregnancy
Simon Collins, HIV i-Base
On 22 June 2018, Janssen issued a Dear Doctor letter (included as next HTB article) against using darunavir/cobicistat during pregnancy. 
This new contraindication is based on significantly reduced plasma levels of darunavir and cobicistat during the second and third trimesters of pregnancy.
Darunavir can still be used during pregnancy, but only when boosted by ritonavir
The new results are from a pharmacokinetic study presented earlier this year in six HIV positive pregnant women and a more recent FDA update. [2, 3]
In summary, the mean exposure (AUC) of darunavir boosted with cobicistat was 56% and 50% lower during the second and third trimesters of pregnancy, respectively, compared with 6 to 12 weeks postpartum. Mean darunavir Cmin concentrations were around 90% lower during the second and third trimesters, compared to postpartum. Exposure of cobicistat was 63% and 49% lower during the second and third trimeters, respectively, as compared to postpartum.
Although another recent FDA update to the darunavir/cobicistat in February 2018 cautioned about low darunavir exposure during the third trimester, the new alert goes further in making pregnancy a contraindication. 
No HIV transmissions to the baby were reported in these studies, but it is unclear whether transmissions have been reported in other settings.
The coformulation of darunavir/cobicisat is marketed as Rezolsta in the EU and Prezcobix in the US.
The single pill fixed dose combination of darunavir/cobicistat/emtricitabine/TAF is marketed as Symtuza.
- Janssen Dear Doctor letter. Darunavir/cobicistat: Increased risk of treatment failure and increased risk of mother-to-child transmission of HIV infection when darunavir and cobicistat co-administered, due to low exposure values during the second and third trimesters of pregnancy. (22 June 2018).
- Crauwels HM et al. Pharmacokinetics of total and unbound darunavir in HIV-1–infected pregnant women receiving a darunavir/cobicistat-based regimen. Poster presented at the 8th International Workshop on HIV & Women, 2-3 March 2018, Boston.
- FDA. Prezcobix pregnancy label update. (05 June 2018).
- US darunavir label updated: drug interactions and pregnancy. HTB February 2018.