No evidence that contaminated nelfinavir led to increased risk of birth abnormalities or cancer

HIV-negative infants potentially exposed in utero to doses of the HIV protease inhibitor nelfinavir (Viracept) contaminated with the toxic compound ethyl methyl sulfone (EMS) did not have an increased risk of birth abnormalities, nor is there any increased risk of cancer, according to French research published in the online edition of AIDS.

“These data are generally reassuring about the health of children exposed in utero to the EMS contamination,” write the authors.

Between May 2007 and July 2008, batches of nelfinavir were contaminated with EMS, a powerful toxin associated with birth abnormalities and an increased risk of cancer. The contamination resulted in the recall of all batches of the drug and ultimately in the manufacturer, Roche, ceasing production of nelfinavir.


in utero

Latin term meaning in the womb.

person years

In a study “100 person years of follow-up” could mean that information was collected on 100 people for one year, or on 50 people for two years each, or on ten people over ten years. In practice, each person’s duration of follow-up is likely to be different.


A poisonous substance.



Relating to the period starting a few weeks before birth and including the birth and a few weeks after birth.

first-line therapy

The regimen used when starting treatment for the first time.

Toxicological analysis of contaminated batches showed that the potential exposure was substantially below levels capable of damaging health. A study of cancer incidence among exposed patients had reassuring findings, showing that the risk of malignancies was no higher than that observed in people taking non-contaminated nelfinavir or other protease inhibitors.

At the time of the recall, nelfinavir was no longer a first-line antiretroviral. However, because of its good safety profile, the drug was a preferred option for the treatment of pregnant women with HIV and the prevention of vertical (mother-to-child) transmission of HIV.

French investigators were concerned that although the levels of EMS contamination may have been non-toxic for children and adults, they may nevertheless have been toxic for embryos and foetuses, especially given that EMS is known to pose a risk of birth abnormalities.

The French Perinatal Cohort routinely gathers data on birth defects and cancer incidence among HIV-exposed infants and therefore provided investigators with a large dataset to determine whether in utero exposure to EMS-contaminated nelfinavir had adverse effects.

The investigators first examined data on birth abnormalities, comparing rates among newborns exposed to nelfinavir during and outside the contamination periods. There was no difference between the two periods, regardless of trimester of exposure to the drug.

Next, the investigators compared cancer incidence among infants and children exposed to nelfinavir in utero outside and during the EMS contamination periods. Incidence was 8.5 per 100,000 person-years of follow-up for infants and children exposed to the drug outside the contamination period, and 0 per 100,000 person-years for those exposed during the contamination period.

“The incidence of malformation was similar to that of the cohort as a whole with different drug exposure,” conclude the authors. “No children developed cancer after 9 years of follow-up.”


Hleyhel M et al. In utero exposure to nelfinavir-EMS. AIDS, online edition. DOI: 10.1097/QAD.0000000000001254, 2016.