Dimethyl Fumarate (Page 4 of 6)

13 NONCLINICAL TOXICOLOGY

13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility

Carcinogenesis
Carcinogenicity studies of dimethyl fumarate (DMF) were conducted in mice and rats. In mice, oral administration of DMF (25, 75, 200, and 400 mg/kg/day) for up to two years resulted in an increase in nonglandular stomach (forestomach) and kidney tumors: squamous cell carcinomas and papillomas of the forestomach in males and females at 200 and 400 mg/kg/day; leiomyosarcomas of the forestomach at 400 mg/kg/day in males and females; renal tubular adenomas and carcinomas at 200 and 400 mg/kg/day in males; and renal tubule adenomas at 400 mg/kg/day in females. Plasma MMF exposure (AUC) at the highest dose not associated with tumors in mice (75 mg/kg/day) was similar to that in humans at the recommended human dose (RHD) of 480 mg/day.
In rats, oral administration of DMF (25, 50, 100, and 150 mg/kg/day) for up to two years resulted in increases in squamous cell carcinomas and papillomas of the forestomach at all doses tested in males and females, and in testicular interstitial (Leydig) cell adenomas at 100 and 150 mg/kg/day. Plasma MMF AUC at the lowest dose tested was lower than that in humans at the RHD.
Mutagenesis
Dimethyl fumarate (DMF) and monomethyl fumarate (MMF) were not mutagenic in the in vitro bacterial reverse mutation (Ames) assay. DMF and MMF were clastogenic in the in vitro chromosomal aberration assay in human peripheral blood lymphocytes in the absence of metabolic activation. DMF was not clastogenic in the in vivo micronucleus assay in the rat.
Impairment of Fertility
In male rats, oral administration of DMF (75, 250, and 375 mg/kg/day) prior to and throughout the mating period had no effect on fertility; however, increases in non-motile sperm were observed at the mid and high doses. The no-effect dose for adverse effects on sperm is similar to the recommended human dose (RHD) of 480 mg/day on a body surface area (mg/m2) basis.
In female rats, oral administration of DMF (20, 100, and 250 mg/kg/day) prior to and during mating and continuing to gestation day 7 caused disruption of the estrous cycle and increases in embryolethality at the highest dose tested. The highest dose not associated with adverse effects (100 mg/kg/day) is twice the RHD on a mg/m2 basis. Testicular toxicity (germinal epithelial degeneration, atrophy, hypospermia, and/or hyperplasia) was observed at clinically relevant doses in mice, rats, and dogs in subchronic and chronic oral toxicity studies of DMF, and in a chronic oral toxicity study evaluating a combination of four fumaric acid esters (including DMF) in rats.

13.2 Animal Toxicology and/or Pharmacology

Kidney toxicity was observed after repeated oral administration of dimethyl fumarate (DMF) in mice, rats, dogs, and monkeys. Renal tubule epithelia regeneration, suggestive of tubule epithelial injury, was observed in all species. Renal tubular hyperplasia was observed in rats with dosing for up to two years. Cortical atrophy and interstitial fibrosis were observed in dogs and monkeys at doses above 5 mg/kg/day. In monkeys, the highest dose tested (75 mg/kg/day) was associated with single cell necrosis and multifocal and diffuse interstitial fibrosis, indicating irreversible loss of renal tissue and function. In dogs and monkeys, the 5 mg/kg/day dose was associated with plasma MMF exposures less than or similar to that in humans at the recommended human dose (RHD).
A dose-related increase in incidence and severity of retinal degeneration was observed in mice following oral administration of DMF for up to two years at doses above 75 mg/kg/day, a dose associated with plasma MMF exposure (AUC) similar to that in humans at the RHD.

14 CLINICAL STUDIES

The efficacy and safety of dimethyl fumarate delayed-release capsules were demonstrated in two studies (Studies 1 and 2) that evaluated dimethyl fumarate delayed-release capsules taken either twice or three times a day in patients with relapsing-remitting multiple sclerosis (RRMS). The starting dose for dimethyl fumarate delayed-release capsules was 120 mg twice or three times a day for the first 7 days, followed by an increase to 240 mg twice or three times a day. Both studies included patients who had experienced at least 1 relapse over the year preceding the trial or had a brain Magnetic Resonance Imaging (MRI) scan demonstrating at least one gadolinium-enhancing (Gd+) lesion within 6 weeks of randomization. The Expanded Disability Status Scale (EDSS) was also assessed and patients could have scores ranging from 0 to 5. Neurological evaluations were performed at baseline, every 3 months, and at the time of suspected relapse. MRI evaluations were performed at baseline, month 6, and year 1 and 2 in a subset of patients (44% in Study 1 and 48% in Study 2).
Study 1: Placebo-Controlled Trial in RRMS
Study 1 was a 2-year randomized, double-blind, placebo-controlled study in 1234 patients with RRMS. The primary endpoint was the proportion of patients relapsed at 2 years. Additional endpoints at 2 years included the number of new or newly enlarging T2 hyperintense lesions, number of new T1 hypointense lesions, number of Gd+ lesions, annualized relapse rate (ARR), and time to confirmed disability progression. Confirmed disability progression was defined as at least a 1 point increase from baseline EDSS (1.5 point increase for patients with baseline EDSS of 0) sustained for 12 weeks.
Patients were randomized to receive dimethyl fumarate delayed-release capsules 240 mg twice a day (n=410), dimethyl fumarate delayed-release capsules 240 mg three times a day (n=416), or placebo (n=408) for up to 2 years. The median age was 39 years, median time since diagnosis was 4 years, and median EDSS score at baseline was 2. The median time on study drug for all treatment arms was 96 weeks. The percentages of patients who completed 96 weeks on study drug per treatment group were 69% for patients assigned to dimethyl fumarate delayed-release capsules 240 mg twice a day, 69% for patients assigned to dimethyl fumarate delayed-release capsules 240 mg three times a day and 65% for patients assigned to placebo groups.
Dimethyl fumarate delayed-release capsules had a statistically significant effect on all of the endpoints described above and the 240 mg three times daily dose showed no additional benefit over the dimethyl fumarate delayed-release capsules 240 mg twice daily dose. The results for this study (240 mg twice a day vs. placebo) are shown in Table 2 and Figure 1.
Table 2: Clinical and MRI Results of Study 1

Dimethyl Fumarate Delayed-Release Capsules 240 mg BID Placebo P-value
Clinical Endpoints N=410N=408
Proportion relapsing (primary endpoint) Relative risk reduction 27% 49%46%<0.0001
Annualized relapse rate Relative reduction 0.17253%0.364 <0.0001
Proportion with disability progression 16%27% 0.0050
Relative risk reduction38%
MRI Endpoints N=152N=165
Mean number of new or newly enlarging T2 lesions over 2 years Percentage of subjects with no new or newly enlarging lesions 2.645%1727%<0.0001
Number of Gd+ lesions at 2 years Mean (median) 0.1 (0)1.8 (0)
Percentage of subjects with 0 lesions 1 lesion 2 lesions 3 to 4 lesions 5 or more lesions 93%5%<1%0<1%62% 10% 8% 9% 11%
Relative odds reduction (percentage) 90%<0.0001
Mean number of new T1 hypointense lesions over 2 years 1.55.6<0.0001

Figure 1: Time to 12-Week Confirmed Progression of Disability (Study 1)

dimethylfumaratedrcapfigure1
(click image for full-size original)

Study 2: Placebo-Controlled Trial in RRMS
Study 2 was a 2-year multicenter, randomized, double-blind, placebo-controlled study that also included an open-label comparator arm in patients with RRMS. The primary endpoint was the annualized relapse rate at 2 years. Additional endpoints at 2 years included the number of new or newly enlarging T2 hyperintense lesions, number of T1 hypointense lesions, number of Gd+ lesions, proportion of patients relapsed, and time to confirmed disability progression as defined in Study 1.
Patients were randomized to receive dimethyl fumarate delayed-release capsules 240 mg twice a day (n=359), dimethyl fumarate delayed-release capsules 240 mg three times a day (n=345), an open-label comparator (n=350), or placebo (n=363) for up to 2 years. The median age was 37 years, median time since diagnosis was 3 years, and median EDSS score at baseline was 2.5. The median time on study drug for all treatment arms was 96 weeks. The percentages of patients who completed 96 weeks on study drug per treatment group were 70% for patients assigned to dimethyl fumarate delayed-release capsules 240 mg twice a day, 72% for patients assigned to dimethyl fumarate delayed-release capsules 240 mg three times a day and 64% for patients assigned to placebo groups.
Dimethyl fumarate delayed-release capsules had a statistically significant effect on the relapse and MRI endpoints described above. There was no statistically significant effect on disability progression. The dimethyl fumarate delayed-release capsules 240 mg three times daily dose resulted in no additional benefit over the dimethyl fumarate delayed-release capsules 240 mg twice daily dose. The results for this study (240 mg twice a day vs. placebo) are shown in Table 3.

Table 3: Clinical and MRI Results of Study 2

Dimethyl Fumarate Delayed-Release Capsules 240 mg BID Placebo P-value
Clinical Endpoints N=359 N=363
Annualized relapse rate Relative reduction 0.22444% 0.401 <0.0001
Proportion relapsing Relative risk reduction 29%34% 41% 0.0020
Proportion with disability progression Relative risk reduction 13%21% 17% 0.25
MRI Endpoints N=147 N=144
Mean number of new or newly enlarging T2 lesions over 2 years Percentage of subjects with no new or newly enlarging lesions 5.127% 17.412% <0.0001
Number of Gd+ lesions at 2 years Mean (median) 0.5 (0.0)2.0 (0.0)
Percentage of subjects with 0 lesions 1 lesion 2 lesions 3 to 4 lesions 5 or more lesions80%11%3%3%3%61%17%6%2%14%
Relative odds reduction (percentage) 74% <0.0001
Mean number of new T1 hypointense lesions over 2 years 3.0 7.0 <0.0001

dimethylfumaratedrcapfigure1

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