Xencor Inc. said its medicine XmAb5871 did not show the desired efficacy in treating a certain form of lupus compared to placebo in a midstage trial, but the results support further study of the medicine.
The Monrovia, Calif.-based biopharmaceutical company is evaluating XmAb5871 to treat systemic lupus erythematosus, an autoimmune disease in which the body's immune system mistakenly attacks healthy tissue.
The phase 2 trial examined patients who had been transferred off immunosuppressive medication and intramuscular steroids and on to either XmAb5871 or placebo. The goal of the trial was to determine whether patients began to see symptoms of the disease again. Half of the 104 patients received XmAb5871 and another half were given a placebo. Two patients treated with XmAb5871 and 10 patients who received the placebo withdrew from the study, while the rest continued treatment.
After 225 days of treatment, the results did not meet statistical significance for the patients receiving the drug, Xencor said in an Oct. 5 press release. Improvement in lupus symptoms was maintained in about 42% of the patients receiving XmAb5871, compared to about 28.6% on placebo. As for the secondary endpoint of the study, patients receiving XmAb5871 did maintain improvement in symptoms for a longer time, about 230 days, compared to 131 days for the placebo.
The company said the safety profile of the drug was consistent with previous trials. Eight serious adverse events occurred in seven XmAb5871-treated patients, and five serious adverse events occurred in four placebo patients. All patients were treated and stabilized.
Systemic lupus erythematosus, the most common form of lupus, is the third indication after rheumatoid arthritis and IgG4-related disease where XmAb5871 has shown promise, according to Xencor President and CEO Bassil Dahiyat. The company will initiate a phase 3 study of the therapy to treat IgG4-related disease, a chronic inflammatory condition characterized by tissue infiltration with lymphocytes and IgG4-secreting plasma cells.
The company is exploring a further study of the therapy for lupus, possibly through a partnership with another entity, Dahiyat said.