Engineering sperm-binding IgG antibodies for the development of an effective nonhormonal female contraception

Bhawana Shrestha, Alison Schaefer, Yong Zhu, Jamal Saada, Timothy M. Jacobs, Elizabeth C. Chavez, Stuart S. Omsted, Carlos A. Cruz-Teran, Gabriela Baldeon Vaca, Kathleen Vincent, Thomas R. Moench, Samuel K. Lai

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


Many women risk unintended pregnancy because of medical contraindications or dissatisfaction with contraceptive methods, including real and perceived side effects associated with the use of exogenous hormones. We pursued direct vaginal delivery of sperm-binding monoclonal antibodies (mAbs) that can limit progressive sperm motility in the female reproductive tract as a strategy for effective nonhormonal contraception. Here, motivated by the greater agglutination potencies of polyvalent immunoglobulins but the bioprocessing ease and stability of immunoglobulin G (IgG), we engineered a panel of sperm-binding IgGs with 6 to 10 antigen-binding fragments (Fabs), isolated from a healthy immune-infertile woman against a unique surface antigen universally present on human sperm. These highly multivalent IgGs (HM-IgGs) were at least 10- to 16-fold more potent and faster at agglutinating sperm than the parent IgG while preserving the crystallizable fragment (Fc) of IgG that mediates trapping of individual spermatozoa in mucus. The increased potencies translated into effective (>99.9%) reduction of progressively motile sperm in the sheep vagina using as little as 33 μg of the 10-Fab HM-IgG. HM-IgGs were produced at comparable yields and had identical thermal stability to the parent IgG, with greater homogeneity. HM-IgGs represent not only promising biologics for nonhormonal contraception but also a promising platform for engineering potent multivalent mAbs for other biomedical applications.

Original languageEnglish (US)
Article numbereabd5219
JournalScience Translational Medicine
Issue number606
StatePublished - Aug 11 2021

ASJC Scopus subject areas

  • Medicine(all)


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