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Recommendations for the Use of Antiretroviral Drugs in Pregnant Women with HIV Infection and Interventions to Reduce Perinatal HIV Transmission in the United States

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Cobicistat (Tybost, COBI)

Last Updated: October 26, 2016; Last Reviewed: October 26, 2016

Cobicistat is classified as Food and Drug Administration Pregnancy Category B.

Animal Studies 

At cobicistat exposures 7 times and 16 times the human systemic exposure, no increases in tumor incidence were seen in male and female mice. In rats, an increased incidence of follicular cell adenomas and/or carcinomas in the thyroid gland was observed at doses up to twice the typical human exposure. The follicular cell findings are considered rat-specific, and not relevant to humans.1

No effect has been seen on fertility in male or female rats.1

Teratogenicity/Developmental Toxicity
Rats and rabbits treated with cobicistat during pregnancy at 1.4 and 3.3 times higher than the recommended human exposure have shown no evidence of teratogenicity.1

Placental and Breast Milk Passage No information is available on placental passage of cobicistat. Studies in rats have shown that cobicistat is secreted in breast milk.2

Human Studies in Pregnancy

Pharmacokinetic studies in pregnancy are limited to a single case report, which found that cobicistat area under the curve was reduced by 44% during the third trimester of pregnancy.3

Placental and Breast Milk Passage
No data are available on placental or breast milk passage of cobicistat in humans.

Teratogenicity/Developmental Toxicity
In the Antiretroviral Pregnancy Registry, no birth defects have been reported in 32 live births with first trimester exposure and 18 live births with second- or third-trimester exposure to cobicistat. The numbers of first-trimester exposures to cobicistat in humans are insufficient to be able to make a risk determination.2

Excerpt from Table 8a
Generic Name
Trade Name
Formulation Dosing Recommendations Use in Pregnancy

Elvitegravir/ Cobicistat/ Tenofovir Disoproxil Fumarate/ Emtricitabine

Elvitegravir/Cobicistat/ Tenofovir Alafenamide/Emtricitabine


Tablet (Tybost):
  • 150 mg

Tablet (Stribild):
  • EVG 150 mg plus COBI 150 mg plus TDF 300 mg plus FTC 200 mg

Tablet (Genvoya):
  • EVG 150 mg plus COBI 150 mg plus TAF 10 mg plus FTC 200 mg

Tablet (Evotaz):
  • ATV 300 mg plus COBI 150 mg

Tablet (Prezcobix):
  • DRV 800 mg plus COBI 150 mg
Standard Adult Dose
  • As an alternative PK booster with atazanavir or darunavir: One tablet (150 mg) once daily with food.
Stribild, Genvoya, Evotaz, Prezcobix:
  • One tablet once daily with food.
PK in Pregnancy:
  • No PK studies in human pregnancy.
Dosing in Pregnancy:
  • Insufficient data to make dosing recommendation.
No data on placental transfer of COBI are available.

Insufficient data to assess for teratogenicity in humans. No evidence of teratogenicity in rats or rabbits.

a Individual antiretroviral drug dosages may need to be adjusted in renal or hepatic insufficiency (for details, see Adult Guidelines, Appendix B, Table 7).

Key to Abbreviations: ATV = atazanavir; COBI = cobicistat; DRV = darunavir; EVG = elvitegravir; FTC = emtricitabine; PK = pharmacokinetic; TAF = tenofovir alafenamide fumarate; TDF = tenofovir disoproxil fumarate


  1. Cobicistat [package insert]. Food and Drug Administration. 2015. Available at Accessed September 21, 2016.
  2. Antiretroviral Pregnancy Registry Steering Committee. Antiretroviral Pregnancy Registry international interim report for 1 Januray 1989–31 July 2015. Wilmington, NC: Registry Coordinating Center. 2015. Available at
  3. Schalkwijk S, Colbers A, Konopnicki D, et al. First reported use of elvitegravir and cobicistat during pregnancy. AIDS. 2016;30(5):807-808. Available at

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