For the past 50 years there have been no new drug treatments approved for systemic lupus erythamatosus (SLE). Now, at last, that situation could soon change. The FDA is currently reviewing one new drug whilst another, epratuzumab, in development by Immunomedics Inc and UCB, is about to start phase III clinical trials after showing promising results in a smaller trial. If successful, it could be available within a few years.
Epratuzumab, a humanised IgG1 monoclonal antibody, treats SLE by a novel mechanism that involves stimulating the CD22 molecule. CD22 plays a role in regulating activity of the immune system and the emergence of auto-immune diseases of which SLE is one.
The drug has recently been studied in EMBLEM, a phase IIb trial. Some of the results of this were both statistically significant and clinically meaningful, according to investigators who presented data at the recent 74th meeting of the American Congress of Rheumatology in Atlanta.
Data from EMBLEM were reported in an oral session at ACR by Dr Daniel Wallace of the UCLA Medical School, Los Angeles, California, USA. EMBLEM was a 12-week study that recruited 227 patients with active SLE, he said. “Most of these patients were very sick at the time they entered the study.”
EMBLEM was essentially designed to identify an optimal dose and dosing schedule for epratuzumab. But results also suggest that in certain dosages the drug will be very effective in suppressing SLE without causing adverse side effects, he noted.
Patients were randomised to receive one of five different doses of epratuzumab ranging from 200mg to 3600mg or placebo in addition to their usual background therapy. Their response to treatment was then monitored at four weekly intervals using two different systems for assessing disease activity – the BILAG (British Isles Lupus Assessment Group) index and the SLEDAI (SLE disease activity index). The SLEDAI is a subjective assessment made from clinicians’ global impressions.
The BILAG index assigns an alphabetic rating to disease activity in eight different organ systems (for example, the musculo-skeletal system is one and the cardio-respiratory system another) based on results of clinical examination, medical history and results of laboratory tests. An A rating points to disease that has flared up and is severe whilst a D rating shows symptoms have completed abated and disease is quiescent. Most of the patients in EMBLEM (71%) had one or more BILAG A ratings at entry. Investigators looked for changes in BILAG ratings as a means of monitoring improvement or worsening in organ systems following treatment.
Dr Wallace told the audience that all doses of epratuzumab with the exception of the highest dose outperformed placebo. The highest dose was thought to have triggered cellular mechanisms that cancelled out the drug’s beneficial effects, he explained. Given that there were six arms in the study, the number of patients in each arm was fairly small. Nevertheless, patients who received a cumulative dose of 2400mg, either by 600mg doses administered weekly or 1200mg every other week, had a statistically significant result (p=0.02) that was also clinically meaningful, he observed. “I am very excited by the results. These patients were quite sick at the start and the degree of improvement we saw was substantial.” The response in the 600mg weekly arm was 45.9% and in the 1200mg every other week arm was 43.2%. This was more than double the 21.1% response seen in the placebo arm.
He added: “We found this drug works quickly, starting by 4 to 8 weeks. It was very effective. By week 12 there was a significant difference in the number of patients on the 600mg weekly dose who had improved their BILAGA/B scores to BILAG D in all six body systems compared to placebo. We also found that epratuzumab was very safe with no new signals to cause concern.” Although adverse events were observed including infections and injection site reactions, these were comparable to adverse events seen in the placebo arm, he commented. For any treatment arm, the discontinuation rate was no higher than 3%.
In a poster also presented at ACR, Dr Kenneth Kalounian, of UCSD School of Medicine, La Jolla, USA, reported that in some body systems, namely CNS and cardiorespiratory, most patients on active treatment with epratuzumab experienced symptom reduction or complete absence of active disease. All patients who received the 600mg weekly dose had improved to BILAG-D by the end of 12 weeks. In the neuropsychiatric system 5 out of 6 patients went from BILAG B to D. Although the number of patients in each arm was small, these were very promising findings, he remarked.
A multinational phase III trial of epratuzumab is now expected to begin early next year.
Written by: Olwen Glynn Owen