Lenabasum Missed Primary Endpoint for dcSSc but Isn't Dead Yet

Although a phase 3 trial of lenabasum did not meet its primary endpoint for treatment of diffuse cutaneous systemic sclerosis (dcSSc), the drug led to more improvement in participants who were not receiving background immunosuppressant therapy during the trial than that seen in participants who received the placebo. Lenabasum also had a favorable safety profile, according to findings presented at the annual European Congress of Rheumatology.

The double-blind, randomized, placebo-controlled trial involved 363 adults who had had dcSSc for up to 6 years. One third of the participants received 5 mg of oral lenabasum, one third received 20 mg, and one third received a placebo. Patients already receiving immunosuppressant therapy could continue to receive it during the trial if the dose had been stable for at least 8 weeks before screening and corticosteroid therapy did not exceed 10 mg prednisone per day or the equivalent.

Dr Robert Spiera

"The decision to allow background immunosuppressant therapies was made to reflect real-world clinical practice," co-principal investigator Robert Spiera, MD, director of the Vasculitis and Scleroderma Program at the Hospital for Special Surgery, New York City, told attendees.

"It is surprising that we do not see any added efficacy of lenabasum in this trial given the fact that the previous phase 2 trial in 42 patients did show a clear benefit of lenabasum over placebo in the same population," Jeska K. de Vries-Bouwstra, MD, PhD, a rheumatologist at Leiden University Medical Center in Leiden, the Netherlands, told Medscape Medical News. "Even more, the clinical response in the phase 2 study was supported by a greater change in gene expression in skin tissue of pathways involved in inflammation and fibrosis with lenabasum as compared to placebo."

Background Immunosuppressants Contribute to Unprecedented Placebo Responses

The researchers compared the ACR CRISS (Combined Response Index in Diffuse Cutaneous Systemic Sclerosis) score and several secondary endpoints at 52 weeks between the 123 participants who received the placebo and the 120 participants who received 20 mg of lenabasum. A total of 60% of the lenabasum group and 66% of the placebo group had a disease duration of 3 or fewer years, and the modified Rodnan skin score (mRSS) was 22 in the lenabasum group and 23.3 in the placebo group at baseline.

A large majority of participants in both groups — 89% in the lenabasum group and 84% in the placebo group — were receiving background immunosuppressant therapy during the trial. Specifically, 53% of each group was taking mycophenolate, and 23% of the lenabasum group and 32% of the placebo group were taking corticosteroids. In addition, 22% of the lenabasum group and 12% of the placebo group were on methotrexate, and 27% of the lenabasum group and 22% of the placebo group were on another immunosuppressant therapy.

Half of the placebo group and 58% of the lenabasum group were taking only one immunosuppressive therapy. About one third of the lenabasum (32%) and placebo (34%) groups were taking two or more immunosuppressive therapies.

The primary endpoint at 52 weeks was not significantly different between the two groups: a CRISS score of 0.888 in the lenabasum group and 0.887 in the placebo group. A CRISS score of 0.6 or higher indicates likelihood that a patient improved on treatment. Patients with significant worsening of renal or cardiopulmonary involvement are classified as not improved (score of 0), regardless of improvements in other core items.

"We had very high CRISS scores in all three groups, and they were comparable in all three groups," Spiera reported. Because improvement in placebo group far exceeded expectations, the researchers were unable to discern the treatment effect of lenabasum on top of the placebo effect.

The placebo group had better outcomes than expected because of the background immunosuppressant therapy, particularly the use of mycophenolate. When the researchers looked only at placebo participants, the CRISS score was 0.936 in the 97 patients receiving background immunosuppressant therapy of any kind and 0.935 in the 29 patients taking only mycophenolate with no other immunosuppressant therapy, compared to 0.417 in the 16 patients not receiving any background therapy.

In a prespecified analysis, the researchers investigated background immunosuppressive therapy as a mediator. The CRISS score for the 10 lenabasum participants not receiving background therapy was 0.811, compared with 0.417 seen in the placebo group patients not on background therapy.

Among the 173 participants taking mycophenolate in particular, the mycophenolate "had a statistically significant improvement on CRISS score that increased with each visit," Spiera reported. The duration of mycophenolate therapy also affected efficacy results.

Patients who had been taking mycophenolate longer saw less improvement in their CRISS score over time. Those taking it more than 2 years at baseline had a CRISS score of 0.86, compared with 0.96 for those taking it for 1-2 years at baseline and 0.98 for those taking it from 6 months to 1 year at baseline. Those who had only been taking mycophenolate for up to 6 months at baseline had a CRISS score of 0.99. Meanwhile, patients not taking any background immunosuppressant therapies only had a CRISS score of about 0.35.

Changes in Secondary Endpoints Followed Same Pattern as CRISS

The secondary endpoints similarly showed no statistically significant difference when comparing the lenabasum and placebo groups overall. These endpoints included change in mRSS score, change in forced vital capacity (FVC) percentage and volume, and change in the Health Assessment Questionnaire Disability Index (HAQ-DI) score.

However, the researchers again found that duration of background therapy affected FVC.

"You were more likely to have declined [in FVC] if you were on placebo and more likely to have improved or stayed stable if you were on lenabasum if you were a patient on more than 2 years of immunomodulatory therapy at baseline," Spiera reported. "There was evidence for an effect of lenabasum on FVC suggested by post-hoc analyses that considered the effect of background immunosuppressive therapies on outcomes, but those results would require confirmation in additional studies to determine the potential of lenabasum for treating patients with diffuse cutaneous systemic sclerosis," Spiera noted in his conclusions.

Serious adverse events occurred in 9.2% of the lenabasum group and 5.8% of the placebo group. Rates of severe adverse events were similar between the lenabasum (14.6%) and placebo (13%) groups.

Is There a Subgroup for Whom Lenabasum Would Be Efficacious?

Although De Vries-Bouwstra of Leiden University Medical Center acknowledged the role of mycophenolate in the trial, she does not think background therapy can totally explain the observation and speculated on other possibilities.

"For example, there were fewer males in the placebo group as compared to the phase 2 study. From previous cohort studies we know that males have higher risk of worsening of skin disease," she said. "In addition, it could be worthwhile to evaluate antibody profiles of the population under study; some subpopulations defined by autoantibody have higher risk for skin progression, while others can show spontaneous improvement."

De Vries-Bouwstra said that although it's not currently appropriate to advocate for lenabasum to treat dcSSc, it may eventually become an additional treatment in those who still show active skin or lung disease after 2 years of mycophenolate treatment if future research identifies a benefit from that application. She would also like to see an evaluation of lenabasum's possible benefits in patients with very early and active inflammatory disease. "Ideally, one could stratify patients based on biomarkers reflecting activation in relevant pathways, for example by using gene expression analysis from skin tissue to stratify," she said.

Jacob M. van Laar, MD, PhD, professor of rheumatology at the University Medical Center Utrecht, the Netherlands, also commented on the potential differences in using the drug in early vs later disease.

Dr Jacob van Laar

"Based on ex vivo analyses of skin samples from systemic sclerosis patients, one would expect such a mechanism of action to be particularly relevant in very early disease, so the observation that it might also be effective at a later disease stage is interesting," van Laar told Medscape Medical News. "We still have a lot to learn about this complex disease."

Given that safety does not appear to be a major concern and there may be a benefit in a subgroup of patients, van Laar also said he hoped "the company is not deterred by the seemingly negative result of the primary endpoint."

Spiera expressed optimism about what this trial's findings have revealed about management of dcSSc.

"Independent of what lenabasum did or didn't do in this trial, I think there's going to be a lot that we're going to learn from this trial and that we're already learning and analyzing right now about treating scleroderma," he told Medscape Medical News.

He reiterated the value of allowing background therapy in the trial to ensure it better replicated real-world clinical practice.

"You're not withholding therapies that we think are probably active from patients with active disease that, once you incur organ damage, is probably not going to be reversible," Spiera said. "The downside is that it makes it harder to see an effect of a drug on top of the background therapy if that background therapy is effective. So what we saw in terms of this absence of benefit from lenabasum really may have been a ceiling effect."

Nevertheless, Spiera said the findings still strongly suggest that lenabasum is an active compound.

"It's not an enormously powerful effect, but it probably has a role as an adjunctive therapy in people on stable background therapy who have either plateaued or are getting worse," he said. "The thing we have to keep in mind also is this was an incredibly safe therapy. It's not immunosuppressive."

The trial was funded by Corbus. Spiera has received grant support or consulting fees from Roche-Genentech, GlaxoSmithKline, Boehringer Ingelheim, Chemocentryx, Corbus, Formation Biologics, Inflarx, Kadmon, AstraZeneca, AbbVie, CSL Behring, Sanofi, and Janssen. De Vries-Bouwstra has received consulting fees from AbbVie and Boehringer Ingelheim and research grants from Galapagos and Janssen. Van Laar has received grant funding or personal fees from Arthrogen, Arxx Therapeutics, AstraZeneca, Bristol-Myers Squibb, Eli Lilly, Gesynta, Leadiant, Merck Sharp & Dohme, Roche, Sanofi, and Thermofisher.

European Alliance of Associations for Rheumatology (EULAR) 2021 Annual Meeting: Abstract OP0171. Presented June 3, 2021.

Tara Haelle is an independent science journalist based in Texas who writes about medical research. Find her at @tarahaelle.

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