Four randomized, controlled, double-blind clinical trials established the efficacy of teriflunomide in patients with relapsing forms of multiple sclerosis. 

Study 1 was a double-blind, placebo-controlled clinical trial that evaluated once daily doses of teriflunomide 7 mg and teriflunomide 14 mg for up to 26 months in patients with relapsing forms of multiple sclerosis. Patients were required to have a diagnosis of multiple sclerosis exhibiting a relapsing clinical course, with or without progression, and to have experienced at least one relapse over the year preceding the trial or at least two relapses over the two years preceding the trial. Patients were required not to have received interferon-beta for at least four months, or any other multiple sclerosis medication for at least six months before entering the study, nor were these medications permitted during the study. Neurological evaluations were to be performed at screening, every 12 weeks until week 108, and after suspected relapses. MRI was to be performed at screening, and at week 24, 48, 72, and 108. The primary endpoint was the annualized relapse rate (ARR).

In Study 1, 1088 patients were randomized to receive teriflunomide 7 mg (n=366), teriflunomide 14 mg (n=359), or placebo (n=363). At entry, patients had an Expanded Disability Status Scale (EDSS) score ≤5.5. Patients had a mean age of 38 years, mean disease duration of 5 years, and mean EDSS at baseline of 2.7. A total of 91% of patients had relapsing remitting multiple sclerosis, and 9% had a progressive form of multiple sclerosis with relapses. The mean duration of treatment was 635, 627, and 631 days for teriflunomide 7 mg, teriflunomide 14 mg, and placebo, respectively. The percentage of patients who completed the study treatment period was 75%, 73%, and 71% for teriflunomide 7 mg, teriflunomide 14 mg, and placebo, respectively. 

There was a statistically significant reduction in ARR for patients who received teriflunomide 7 mg or teriflunomide 14 mg, compared to patients who received placebo (see Table 2). There was a consistent reduction of the ARR noted in subgroups defined by sex, age group, prior multiple sclerosis therapy, and baseline disease activity. 

There was a statistically significant reduction in the relative risk of disability progression at week 108 sustained for 12 weeks (as measured by at least a 1-point increase from baseline EDSS ≤5.5 or a 0.5 point increase for those with a baseline EDSS >5.5) in the teriflunomide 14 mg group compared to placebo (see Table 2 and Figure 1). 

The effect of teriflunomide on several magnetic resonance imaging (MRI) variables, including the total lesion volume of T2 and hypointense T1 lesions, was assessed in Study 1. The change in total lesion volume from baseline was significantly lower in the teriflunomide 7 mg and teriflunomide 14 mg groups than in the placebo group. Patients in both teriflunomide groups had significantly fewer gadolinium-enhancing lesions per T1-weighted scan than those in the placebo group (see Table 2).

Figure 1: Kaplan-Meier Plot of Time to Disability Progression Sustained for 12 Weeks (Study 1)

Study 2 was a double-blind, placebo-controlled clinical trial that evaluated once daily doses of teriflunomide 7 mg and teriflunomide 14 mg for up to 40 months in patients with relapsing forms of multiple sclerosis. Patients were required to have a diagnosis of multiple sclerosis exhibiting a relapsing clinical course and to have experienced at least one relapse over the year preceding the trial, or at least two relapses over the two years preceding the trial. Patients were required not to have received any multiple sclerosis medication for at least three months before entering the trial, nor were these medications permitted during the trial. Neurological evaluations were to be performed at screening, every 12 weeks until completion, and after every suspected relapse. The primary end point was the ARR. 

A total of 1165 patients received teriflunomide 7 mg (n=407), teriflunomide 14 mg (n=370), or placebo (n=388). Patients had a mean age of 38 years, a mean disease duration of 5 years, and a mean EDSS at baseline of 2.7. A total of 98% of patients had relapsing remitting multiple sclerosis, and 2% had a progressive form of multiple sclerosis with relapses. The mean duration of treatment was 552, 567, and 571 days for teriflunomide 7 mg, teriflunomide 14 mg, and placebo, respectively. The percentage of patients who completed the study treatment period was 67%, 66%, and 68% for teriflunomide 7 mg, teriflunomide 14 mg, and placebo, respectively.

There was a statistically significant reduction in the ARR for patients who received teriflunomide 7 mg or teriflunomide 14 mg compared to patients who received placebo (see Table 3). There was a consistent reduction of the ARR noted in subgroups defined by sex, age group, prior multiple sclerosis therapy, and baseline disease activity. 

There was a statistically significant reduction in the relative risk of disability progression at week 108 sustained for 12 weeks (as measured by at least a 1-point increase from baseline EDSS ≤5.5 or a 0.5 point increase for those with a baseline EDSS >5.5) in the teriflunomide 14 mg group compared to placebo (see Table 3 and Figure 2).

Figure 2: Kaplan-Meier Plot of Time to Disability Progression Sustained for 12 Weeks (Study 2)

Study 3 was a double-blind, placebo-controlled clinical trial that evaluated once daily doses of teriflunomide 7 mg and teriflunomide 14 mg for up to 108 weeks in patients with relapsing multiple sclerosis. Patients were required to have had a first clinical event consistent with acute demyelination occurring within 90 days of randomization with 2 or more T2 lesions at least 3 mm in diameter that were characteristic of multiple sclerosis. A total of 614 patients received teriflunomide 7 mg (n=203), teriflunomide 14 mg (n=214), or placebo (n=197). Patients had a mean age of 32 years, EDSS at baseline of 1.7, and mean disease duration of two months. The proportion of patients free of relapse was greater in the teriflunomide 7 mg (70.5%, p<0.05) and teriflunomide 14 mg (72.2%, p<0.05) groups than in the placebo group (61.7%). 

The effect of teriflunomide on MRI activity was also demonstrated in Study 4, a randomized, double-blind, placebo-controlled clinical trial of multiple sclerosis patients with relapse. In Study 4, MRI was to be performed at baseline, 6 weeks, 12 weeks, 18 weeks, 24 weeks, 30 weeks, and 36 weeks after treatment initiation. A total of 179 patients were randomized to teriflunomide 7 mg (n=61), teriflunomide 14 mg (n=57), or placebo (n=61). Baseline demographics were consistent across treatment groups. The primary endpoint was the average number of unique active lesions/MRI scan during treatment. The mean number of unique active lesions per brain MRI scan during the 36-week treatment period was lower in patients treated with teriflunomide 7 mg (1.06) and teriflunomide 14 mg (0.98) as compared to placebo (2.69), the difference being statistically significant for both (p=0.0234 and p=0.0052, respectively).