An immunomodulator known as AS101 has been shown to prevent ovarian follicle “burnout” in mice receiving chemotherapy with cyclophosphamide.

Lital Kalich-Philosoph of the Fertility Preservation Research Laboratory at Chaim Sheba Medical Center in Tel Hashomer, Israel, and colleagues discovered that cyclophosphamide, an alkylating agent, causes the overactivation of follicles resting in the ovaries. As the group explained in Science Translational Medicine, the activation of too many follicles leads to a loss, or “burning out,” of the ovarian egg reserve. Cyclophosphamide also kills active growing follicles, contributing further to infertility in females undergoing chemotherapy with this drug.

In addition to identifying accelerated follicle activation as the likely culprit behind cyclophosphamide-induced loss of ovarian reserve, Kalich-Philosoph and coinvestigators found that administering AS101 along with cyclophosphamide increased follicle reserve and rescued fertility following treatment. 

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“By preventing [accelerated primordial follicle] activation, AS101 shows potential as an ovarian-protective agent, which may be able to preserve fertility in female cancer patients,” concluded the researchers.

The addition of AS101 also increased the efficacy of cyclophosphamide against breast cancer cell lines.