XOMA 213

XOMA 213 is a first-in-class allosteric inhibitor of prolactin action. It is a humanized IgG1-Kappa monoclonal antibody that binds to the extracellular domain of the human prolactin receptor with high affinity at an allosteric site. The antibody has been shown to inhibit prolactin-mediated signaling, and it is potent and similarly active against several animal and human prolactin receptors.

We discovered XOMA 213 under our collaboration with Novartis AG (“Novartis,” formerly Chiron Corporation), and we exercised our right to bring the product back into our portfolio to develop it for diseases of hyperprolactinemia. In particular, our product can be developed for treating certain prolactinomas, conditions of benign tumors on the pituitary gland that lead to hyperprolactinemia-induced sexual dysfunction, infertility, and osteoporosis, as well as treatment of anti-psychotic-induced hyperprolactinemia, a side effect seen in patients treated with commonly used antipsychotics, antidepressants, and pain medications.


For the nearly 20 percent of 140,000 prolactinoma patients in the United States, existing therapies are poorly tolerated or not responsive to treatment with existing therapy. Anti-psychotic-induced hyperprolactinemia is a side effect seen in patients treated with commonly used antipsychotics, antidepressants, and pain medications. As patients exhibit the same signs and symptoms as prolactinoma, compliance with anti-psychotic therapies is poor. Currently available therapies to address these side effects can worsen psychosis.

Stage of Development

We initiated a Phase 2 POC study for XOMA 213 in June 2016. In April 2017, we achieved positive Phase 2 POC results for XOMA 213 in physiological hyperprolactinemia (HPRL). The results of the study indicate XOMA 213, when given as a single 700mg intravenous infusion during the first day post-partum, was effective in suppressing milk secretion, as well as breast engorgement and pain in 100 percent of the treated women. In addition, none of the treated women experienced rebound breast symptomatology during the 21-day study period. While the study was not intended or powered to show statistical significance, it demonstrated XOMA 213 was safe and well tolerated, caused no significant adverse events (SAEs), showed favorable pharmacokinetics with a terminal half-life of two weeks and demonstrated target (prolactin receptor) engagement and mechanism of action confirmation by serum prolactin profiling.