New and future therapies for lupus nephritis

RITUXIMAB: PROMISING BUT UNPROVEN

Rituximab (Rituxan) was originally approved to treat tumors, then rheumatoid arthritis, and most recently vasculitis. Evidence thus far is mixed regarding its use as a treatment for lupus nephritis. Although randomized clinical trials have not found it to be superior to standard regimens, there are many signs that it may be effective.

Rituximab in uncontrolled studies

Terrier et al¹³ analyzed prospective data from 136 patients with systemic lupus erythematosus, most of whom had renal disease, from the French Autoimmunity and Rituximab registry. Response occurred in 71% of patients using rituximab, with no difference found between patients receiving rituximab monotherapy and those concomitantly receiving immunosuppressive agents.

Melander et al¹⁴ retrospectively studied 19 women and 1 man who had been treated with rituximab for severe lupus nephritis and followed for at least 1 year. Three patients had concurrent therapy with cyclophosphamide, and 10 patients continued rituximab as maintenance therapy; 12 patients had lupus nephritis that had been refractory to standard treatment, and 6 had relapsing disease.

At a median follow-up of 22 months, 12 patients (60%) had achieved complete or partial renal remission.

Condon et al¹⁵ treated 21 patients who had severe lupus nephritis with two doses of rituximab and IV methylprednisolone 2 weeks apart, then maintenance therapy with mycophenolate without any oral steroids. At a mean follow-up of 35 months ( ± 14 months), 16 (76%) were in complete remission, with a mean time to remission of 12 months. Two (9.5%) achieved partial remission. The rate of toxicity was low.

Thus, rituximab appears promising in uncontrolled studies.

Placebo-controlled trials fail to prove rituximab effective

LUNAR trial. On the other hand, the largest placebo-controlled trial to evaluate rituximab in patients with proliferative lupus nephritis, the Lupus Nephritis Assessment With Rituximab (LUNAR) trial¹⁶ found differences in favor of rituximab, but none reached statistical significance. The trial randomized 140 patients to receive either mycophenolate plus periodic rituximab infusions or mycophenolate plus placebo infusions for 1 year. All patients received the same dosage of glucocorticoids, which was tapered over the year.

At the end of 1 year, the groups were not statistically different in terms of complete renal response and partial renal response. Rituximab appeared less likely to produce no response, but the difference was not statistically significant.

African Americans appeared to have a higher response rate to rituximab (70% in the rituximab group achieved a response vs 45% in the control group), but again, the difference did not reach statistical significance, and the total study population of African Americans was only 40.

Rituximab did have a statistically significant positive effect on two serologic markers at 1 year: levels of anti-dsDNA fell faster and complement rose faster. In addition, rates of adverse and serious adverse events were similar between the two groups, with no new or unexpected “safety signals.”

This study can be interpreted in a number of ways. The number of patients may have been too small to show significance and the follow-up may have been too short. On the other hand, it may simply not be effective to add rituximab to a full dose of mycophenolate and steroids, an already good treatment.

EXPLORER trial. Similarly, for patients with lupus without nephritis, the Exploratory Phase II/III SLE Evaluation of Rituximab (EXPLORER) trial¹⁷ also tested rituximab against a background of an effective therapeutic regimen and found no additional benefit. This study had design problems similar to those of the LUNAR trial.

Rituximab as rescue therapy

The evidence so far indicates that rituximab may have a role as rescue therapy for refractory or relapsing disease. Rituximab must be used with other therapies, but maintenance corticosteroid therapy is not necessary. Its role as a first-line agent in induction therapy for lupus nephritis remains unclear, although it may have an important role for nonwhites. In general, it has been well tolerated. Until a large randomized trial indicates otherwise, it should not be used as a first-line therapy.

The US Food and Drug Administration (FDA) sent out a warning about the danger of progressive multifocal leukoencephalopathy as an adverse effect of rituximab and of mycophenolate, but this does not appear to be a major concern for most patients and is only likely to occur in those who have been over-immunosuppressed for many years.

MULTITARGET THERAPY

The concept of using multiple drugs simultaneously—such as mycophenolate, steroids, and rituximab—is increasingly being tried. Multi-target therapy appears to offer the advantages of combining different modes of action with better results, and it offers fewer side effects because dosages of each individual drug can be lower when combined with other immunosuppressives.

Bao et al¹⁸ in China randomly assigned 40 patients with diffuse proliferative and membranous nephritis to 6 to 9 months of induction treatment with either multitarget therapy (mycophenolate, tacrolimus [Prograf], and glucocorticoids) or IV cyclophosphamide. More complete remissions occurred in the multitarget therapy group, both at 6 months (50% vs 5%) and at 9 months (65% vs 15%). Most adverse events were less frequent in the multitarget therapy group, although three patients (15%) in the multitarget therapy group developed new-onset hypertension vs none in the cyclophosphamide group.

NEW MEDICATIONS

Entirely new classes of drugs are being developed with immunomodulatory effects, including tolerance molecules, cytokine blockers, inhibitors of human B lymphocyte stimulator, and costimulatory blockers.

Belimumab offers small improvement for lupus

Belimumab (Benlysta) is a human monoclonal antibody that inhibits the biologic activity of human B lymphocyte stimulator; it has recently been approved by the FDA for lupus nephritis. In a worldwide study,¹⁹ 867 patients with systemic lupus erythematosus were randomized to receive either belimumab (1 mg/kg or 10 mg/kg) or placebo.

The primary end point was the reduction of disease activity by a scoring system (SELENA-SLEDAI) that incorporated multiple features of lupus, including arthritis, vasculitis, proteinuria, rash, and others. Patients in the belimumab group had better outcomes, but the results were not dramatic. Because the drug is so expensive (about $25,000 per year) and the improvement offered is only incremental, this drug will not likely change the treatment of lupus very much.

Moreover, patients with lupus nephritis were not included in the study, but a new study is being planned to do so. Improvement is harder to demonstrate in lupus nephritis than in rheumatoid arthritis and systemic lupus erythematosus: significant changes in creatinine levels and 24-hour urinary protein must be achieved, rather than more qualitative signs and symptoms of joint pain, rash, and feeling better. Although belimumab is still unproven for lupus nephritis, it might be worth trying for patients failing other therapy.

Laquinimod: A promising experimental drug

Laquinimod is an oral immunomodulatory drug with a number of effects, including down-regulating major histocompatability complex II, chemokines, and adhesion-related molecules related to inflammation. It has been studied in more than 2,500 patients with multiple sclerosis. Pilot studies are now being done for its use for lupus nephritis. If it shows promise, a large randomized, controlled trial will be conducted.

Abatacept is in clinical trials

Abatacept (Orencia), a costimulation blocker, is undergoing clinical trials in lupus nephritis. Results should be available shortly.