IFB-088 and Riluzole Combination in Bulbar-Onset ALS: Safety Established but Efficacy Challenges Remain

Novel Combination Therapy Tested in Phase 2 Trial for Bulbar-Onset ALS

Results from a completed Phase 2 clinical trial investigating IFB-088 (icerguastat) in combination with riluzole for patients with bulbar-onset amyotrophic lateral sclerosis (ALS) have recently been published. The international, randomized, double-blind, placebo-controlled study, sponsored by InFlectis BioScience, enrolled 51 patients across multiple centers in France and Italy to assess the safety and efficacy of this novel combination therapy. Patients were randomized in a 2:1 ratio to receive either IFB-088 50 mg/day plus riluzole 100 mg/day or placebo plus riluzole 100 mg/day over a 6-month treatment period. The study, identified as NCT05508074, focused primarily on safety outcomes while also exploring several efficacy endpoints through validated ALS assessment tools. IFB-088, also known as icerguastat, represents an investigational approach to addressing neurodegenerative processes in ALS, a rapidly progressive and fatal neurodegenerative disorder characterized by motor neuron degeneration. This trial specifically targeted patients with bulbar-onset ALS, a form of the disease that initially affects speech and swallowing functions and is often associated with more rapid progression.

The trial design incorporated a comprehensive assessment schedule, with patients undergoing clinic visits at randomization, at 2 weeks, and at months 1, 3, and 6, with additional monitoring between these visits. Inclusion criteria specified that patients must have a diagnosis of probable or definite ALS according to the revised El Escorial criteria, with symptoms onset within 18 months prior to screening, and a slow vital capacity (SVC) greater than 60% of predicted value. All patients were required to be on stable riluzole therapy (100 mg/day) for at least one month prior to enrollment. The primary endpoint focused on safety, measuring the incidence, grade, and relationship to IFB-088 for treatment-emergent adverse events (TEAEs), serious adverse events (SAEs), and adverse events of special interest (AESIs). Secondary endpoints encompassed a wide range of efficacy measurements including the ALS Functional Rating Scale Revised (ALSFRS-R), ALS Milano-Torino Staging (ALS_MITOS), and King's College Scale (ALS Staging Form), as well as respiratory function assessed through slow vital capacity and arterial blood gases. The study also evaluated changes in biomarkers including TDP-43, neurofilament light chain, and various inflammation markers, alongside pharmacokinetic parameters and quality of life measurements using the ALS Assessment Questionnaire (ALSAQ-40).

Safety Profile: How Did IFB-088 Perform in Combination with Riluzole?

Safety data from the trial showed that 25 out of 34 patients (73.5%) in the IFB-088 group experienced treatment-emergent adverse events compared to 10 out of 17 patients (58.8%) in the placebo group. Thirteen patients (38.2%) in the IFB-088 group had adverse events that were considered related to the study drug versus four patients (23.5%) in the placebo group. Serious adverse events occurred in eight patients (23.5%) receiving IFB-088 plus riluzole and in four patients (23.5%) receiving placebo plus riluzole. Of these serious events, two in the IFB-088 group were considered related to the study drug, while none in the placebo group were deemed related to treatment. The trial reported five fatal events (14.7%) in the IFB-088 arm and two fatal events (11.8%) in the placebo arm, with two of the fatal events in the IFB-088 group assessed as related to the study drug. Grade 3 or higher adverse events were observed in 10 patients (29.4%) in the treatment group compared to three patients (17.6%) in the placebo group. Temporary discontinuation of study drug due to adverse events was reported in one patient from each group, while three patients (8.8%) in the IFB-088 group discontinued treatment permanently due to adverse events, with no permanent discontinuations in the placebo group.

Efficacy Outcomes Show No Significant Functional Improvement

Efficacy outcomes revealed no statistically significant differences between the treatment groups in the key functional and respiratory parameters assessed. The ALSFRS-R scores, which measure functional capacity across various domains, showed no significant difference between groups at the 6-month assessment (adjusted mean difference -0.33, 95% CI -7.27 to 6.60, p=0.923). A post hoc analysis adjusted for baseline neurofilament light chain levels similarly showed no significant treatment effect (mean difference 1.5, 95% CI -5.1 to 8.2, p=0.65). The ALS_MITOS scores, which evaluate functional loss across key domains, and the King's College Scale scores also failed to demonstrate significant differences between the treatment groups. Respiratory function parameters, including slow vital capacity and arterial blood gases measurements, showed similar trajectories in both groups throughout the study period. Analysis of neurofilament light chain, a biomarker of neuronal damage, revealed no significant difference in the change from baseline to 6 months between the treatment and placebo groups (adjusted geometric mean ratio 1.04, 95% CI 0.89-1.21, p=0.609). Several inflammation biomarkers were assessed, including GDF15, MCP1, BDNF, and TGFb1, though many inflammation markers were below the detection limit, limiting comprehensive analysis of the immunological effects of the treatment.

Pharmacokinetic Profile and Patient-Reported Outcomes

Pharmacokinetic analyses provided insights into the properties of IFB-088 in the ALS patient population. The area under the curve (AUC) for IFB-088 was measured at 63 ng.h/mL with a geometric coefficient of variation of 61%, while its metabolite IFB-139 showed an AUC of 69 ng.h/mL with a geometric coefficient of variation of 48.9%. Maximum observed plasma concentration (Cmax) for IFB-088 was 12 ng/mL with a geometric coefficient of variation of 66.4%, and for the metabolite IFB-139, Cmax was also 12 ng/mL with a coefficient of variation of 45.9%. The time to reach maximum concentration (Tmax) was 1.0 hours for both the parent compound and its metabolite. The terminal half-life (t1/2) of IFB-088 was determined to be 4.62 hours, while its metabolite exhibited a longer half-life of 7.9 hours. The apparent systemic clearance (CL/F) of IFB-088 was calculated at 580 L/h, and the apparent volume of distribution was 3722 L. These pharmacokinetic parameters provide valuable information about the drug's behavior in patients with ALS, which may inform future dose optimization and administration schedules. Patient-reported outcomes assessed through the ALSAQ-40 questionnaire showed deterioration in quality of life in both groups from baseline to 6 months, with the IFB-088 group having a mean score change from 40.7 to 67.1 and the placebo group changing from 39.5 to 61.4.

What Can We Learn from This Trial Despite Negative Efficacy Results?

The completion of this Phase 2 trial represents an important step in the clinical development of potential therapies for bulbar-onset ALS, a particularly challenging form of the disease with limited therapeutic options. While the study did not demonstrate significant efficacy of IFB-088 in combination with riluzole compared to riluzole alone, it provides valuable safety and pharmacokinetic data that could inform future investigations. The trial had certain limitations, including the relatively small sample size typical of Phase 2 studies and challenges with biomarker analyses that led to numerous below-limit-of-quantification results requiring cautious interpretation. Additionally, the assessment of body composition could not be properly evaluated due to late availability of the necessary devices. The study's focus on bulbar-onset ALS, which represents a specific subtype of the disease with potentially distinct pathophysiological mechanisms, may limit the generalizability of findings to the broader ALS population. Despite these limitations, the detailed characterization of adverse events and the comprehensive assessment of functional outcomes contribute meaningful data to the understanding of therapeutic approaches in ALS. Could the insights from this trial influence the design of future studies investigating IFB-088 or similar compounds in ALS? Might certain subgroups of patients potentially benefit more from this treatment approach, warranting further investigation with more refined patient selection criteria? How might the pharmacokinetic data inform potential dose adjustments or alternative administration schedules that could potentially enhance efficacy while maintaining an acceptable safety profile?