UCB and Immunomedics (NASDAQ: IMMU) expect top-line data from two Phase III trials (EMBODY 1 and EMBODY 2) of epratuzumab in 2015H1. Immunomedics’ fate hangs on the EMBODY trials, but the Phase IIb results that supported the EMBODY trials were not really all that good.
In May 2006, Immunomedics licensed epratuzumab to UCB for the treatment of non-cancer indications. Under the Amendment Agreement in December 2011, Immunomedics is entitled to receive up to $425 million in milestone payments and royalties ranging from 15-25% of net sales.
Epratuzumab is a humanized monoclonal antibody targets CD22, an antigen found on the surface of B cells. UCB is currently testing epratuzumab in systemic lupus erythematosus (SLE), an autoimmune disease affecting about one in 1,000 people.
GlaxoSmithKline’s anti-BAFF monoclonal antibody belimumab is the first new SLE drug in 50 years. The drug is only marginally effective and generated sales of £173 million in 2014. There is ample room for epratuzumab to take share.
In the Phase IIb trial (EMBLEM), SLE patients treated with 600 mg weekly of epratuzumab reported a 45.9% response rate compared with a 21.1% response rate for patients treated with placebo. The data look pretty good, but there is no correlation between dose and response.
Analyst Avik Roy of Monness Crespi Hardt suggested:
Typically, an active drug generates more responses as the dose goes up. In trials where the response goes down as the dose goes up, the positive signal is usually the product of statistical noise, rather than of a true biological effect.
UCB and Immunomedics’ scientists just said that the mechanisms responsible for the low response rate seen with the highest tested dose require further investigation. In December 2010, UCB launched the EMBODY trials to assess the efﬁcacy and safety of 600 mg weekly and 1200 mg Q2W regimens.
A second concern is that 21.6% of patients in the 600 mg weekly group discontinued the study compared to 5.3% from placebo. Dropouts may increase the risk of overall trial failure.
 Ann Rheum Dis. 2014, 73(1), 183-190.