Rebif Solution for Injection in Pre-Filled Syringes - Pharmaceutical Information, Clinical Trials, Detailed Pharmacology, Toxicology.
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Rebif Solution for Injection in Pre-Filled Syringes - Scientific Information

Manufacture: EMD Serono, Inc
Country: Canada
Condition: Multiple Sclerosis Fatigue (Fatigue)
Class: Immunostimulants, Interferons
Form: Liquid solution, Subcutaneous (SC)
Ingredients: interferon beta-1a, mannitol, benzyl alcohol, poloxamer-188, methionine

Pharmaceutical Information

Proper or Common Name: BAN: Interferon beta-1a
INN: Interferon beta-1a
USAN: Interferon beta-1a
Structural Formula: The full amino acid sequence is as follows:
1 Met-Ser-Tyr-Asn-Leu-Leu-Gly-Phe-Leu-Gln
11 Arg-Ser-Ser-Asn-Phe-Gln-Cys-Gln-Lys-Leu
21 Leu-Trp-Gln-Leu-Asn-Gly-Arg-Leu-Glu-Tyr
31 Cys-Leu-Lys-Asp-Arg-Met-Asn-Phe-Asp-Ile
41 Pro-Glu-Glu-Ile-Lys-Gln-Leu-Gln-Gln-Phe
51 Gln-Lys-Glu-Asp-Ala-Ala-Leu-Thr-Ile-Tyr
61 Glu-Met-Leu-Gln-Asn-Ile-Phe-Ala-Ile-Phe
71 Arg-Gln-Asp-Ser-Ser-Ser-Thr-Gly-Trp-Asn*
81 Glu-Thr-Ile-Val-Glu-Asn-Leu-Leu-Ala-Asn
91 Val-Tyr-His-Gln-Ile-Asn-His-Leu-Lys-Thr
101 Val-Leu-Glu-Glu-Lys-Leu-Glu-Lys-Glu-Asp
111 Phe-Thr-Arg-Gly-Lys-Leu-Met-Ser-Ser-Leu
121 His-Leu-Lys-Arg-Tyr-Tyr-Gly-Arg-Ile-Leu
131 His-Tyr-Leu-Lys-Ala-Lys-Glu-Tyr-Ser-His
141 Cys-Ala-Trp-Thr-Ile-Val-Arg-Val-Glu-Ile
151 Leu-Arg-Asn-Phe-Tyr-Phe-Ile-Asn-Arg-Leu
161 Thr-Gly-Tyr-Leu-Arg-Asn

* Asn-80 N-glycosylation site
Molecular Weight: Approximately 22,500 daltons, identical to the natural human IFN-beta
Physical Form:

IFN-beta-1a is a glycoprotein of 166 amino acids, it has 3 cysteines at positions 17, 31 and 141, a single disulphide bridge and an N-linked carbohydrate moiety primarily of the biantennary complex type attached to Asn-80.

 Bulk hIFN-beta-1a is a clear, colourless to yellowish solution.

pH:  3.5 – 4.5 for the pre-filled syringe/3.5 - 4.1 for the pre-filled cartridge


Solution for Injection in a Pre-Filled Cartridge

The liquid formulation is supplied in cartridges containing 1.5 mL of solution. Each cartridge contains Interferon beta-1a, mannitol, poloxamer-188, methionine, benzyl alcohol and 0.01 M sodium acetate buffer, as indicated in the table below.

Interferon beta-1a M Mannitol P Poloxamer-188 M Methionine B Benzyl alcohol 0.01M Sodium
acetate buffer
66 μg 8 83.25 mg 0 0.93 mg 0 0.22 mg 9 9.25 mg q q.s. to 1.5 mL
132 μg 8 83.25 mg 0 0.93 mg 0 0.22 mg 9 9.25 mg q q.s. to 1.5 mL

Clinical Trials

REBIF has been tested in seven large, well-controlled studies of 3256 patients with 2296 on active therapy.

Study No. Trial Design Study Subjects (n=number) and Gender Dose of IFN-beta-1a Route of Administration Duration of Treatment Gender (%) Mean Age (Range) Formulation of REBIF
GF 6613 (phase II) Randomized, open label, comparative 68 males and females 11 µg;, 33 µg 3x / week (untreated observation followed by treatment) SC 6 months. untreated lead-in, followed by 6 months treatment Female: 69.1 Male: 30.9 30.5 (15-44) REBIF HSA-containing
GF 6789 - PRISMS (phase III) Randomized, double-blind, placebo-controlled 560 males and females 22 Вµg, 44 Вµg or placebo 3x / week SC 2 years + 2-year extension (Total openlabelfollowup 8 years) Female: 75.6 Male: 24.4 36.2 (20-55) REBIF HSA-containing
В GF 6954 - SPECTRIMS (phase III) Randomized, double-blind, placebo-controlled 619 males and females 22 Вµg, 44 Вµg or placebo 3x / week SC 3 years + 3 years extension Female: 63 Male: 37 42.8 (19-56) REBIF HSA-containing
GF 6976 (phase III) Randomized, double-blind, placebo-controlled 371 males and females 22 Вµg or placebo1x / week SC В 3 years Female: 59.6 Male: 40.4 45.7 (21.6-65) REBIF HSA-containing
GF 7480 - ETOMS (phase III) Randomized, double-blind, placebo-controlled 309 males and females randomized, 308 received treatment 22 Вµg or placebo1x / week SC 2 years + two 1-year treatment extensions В  Female: 64 Male: 36 29 (18-45) REBIF HSA-containing
GF 7999 - OWIMS (phase III) Randomized, double-blind, placebo-controlled 293 males and females 22 Вµg, 44 Вµg or placebo1x / week SC 1 year + 2 years extension Female : 75 Male : 25 36 (19-51) REBIF HSA-containing
GF 8000 (continuation of GF 6613, phase II) Randomized, open label comparative 67 males and females 11 Вµg or 33 Вµg 3x / week SC 1.5 years Female : 69.1 Male : 30.9 30.7 (15-44) REBIF HSA-containing
IMP 21125 EVIDENCE (phase III) Randomized, open label comparative 677 males and females REBIF 44 Вµg tiw (n=338) or AVONEX 30 Вµg qw (n=338) SC vs IM 24 weeks + 24 weeks extension. (followed by REBIF only extension for 96 weeks) Female : 74.7 Male : 25.3 37.9 (18-55) REBIF HSA-containing
IMP 22930 (LTFU toGF 6789, phase IV) Non-randomized, retrospective and punctual LTFU 560 patients in the original PRISMS Study (No. GF 6793); 382 of those 560 patients were in the PRISMS LTFU study (IMP 22930), and 274 of those 382 patients had EDSS data available. None (patients could continue onREBIF or switch to another diseasemodifying drug) NA 2 years + 2-year extension (Total openlabel followup 8 years) В  В Female : 69.5 Male : 30.5 38 (18.1-53.4) REBIF HSA-containing
IMP 22982 (phase IIIb) Randomized, open label comparative 1883 males and females REBIF 44 Вµg tiw with or without RebijectMini, an auto-injector SC Minimum of 12 weeks treatment Female : 1404 Male : 421 42.6 (17-74) REBIF HSA-containing
IMP 24207 (phase IV) Non-randomized, open label prospective 163 males and females REBIF 44 Вµg tiw and influenza vaccine (single injection) SC 29 days Female : 80.4 Male : 19.6 42.3 (25-55) REBIF HSA-containing
IMP 24735 (phase IV) Randomized, open label comparative 764 males and females REBIF 44 Вµg tiw or Copaxone 20 mg qd SC 96 weeks Female : 69 Male :31 36.8 (17-61) REBIF HSA-containing
24810 (phase IV) Single-arm, open label 460 males and females REBIF 44 Вµg tiw (clone 484-39) SC 48 weeks Female : 73.4 Male : 26.6 В  36 (19-58) New clone for IFN-beta-1a production (484-39) with HSA as excipient
25632- REBIF HSA-free Formulation (phase IIIb) Single-arm, open label 260 males and females REBIF44 Вµg tiw (clone 484-39 in FBS-free/HSA-free formulation) SC 96 weeks Female : 71.5 Male : 28.5 34.9 (18-58) REBIF HSA-free
27025 - REFLEX (phase IIIb) Randomized, double-blind, placebo-controlled, multi-center 158 males and 332 females REBIF 44 Вµg tiw and ow SC 24 months, 1-year open label extension Female: 64.2 Male: 45.8 29.0 (17-51) REBIF HSA-free

Study GF6789 (PRISMS: Prevention of Relapses and Disability by Interferon -1a Subcutaneously in Relapsing-Remitting Multiple Sclerosis)

A total of 560 patients diagnosed with clinically definite or laboratory-supported relapsing-remitting multiple sclerosis EDSS 0 -5 with at least a 1-year history before study entry and a history of 2 or more acute exacerbations in the 2 years prior to study entry were enrolled and randomized to 3 treatments (placebo, 22 μg REBIF, or 44 μg REBIF) in a ratio of 1:1:1. About 90% of patients completed the 2 years of treatment, and entered the extension phase: 167 from the original 44 μg tiw group, 167 from the original 22 µg tiw group, and 172 from the original placebo group. Prior to the start of the extension phase and without knowledge of study results, all patients from the original placebo group were re-randomized to receive either 22 or 44 μg tiw (85 randomized to 22 g, and 87 randomized to 44 μg). The patients from the original 22 and 44 μg tiw groups continued their treatment as originally randomized. Of the original 560 patients enrolled in the study, 445 (79%) remained in the study to the end of year 4. Less than 10 % of patients treated with active therapy withdrew for adverse events over 4 years.

REBIF 66 g weekly (22 µg, 3x/week) and 132 g weekly (44 μg, 3x/week) had a significant effect on the primary outcome measure by reducing relapse count compared to placebo. The relapse rate reduction continued during years 3 and 4 of therapy. Patients converting to REBIF from placebo demonstrated a 52-53% reduction in relapse rate compared to years on placebo. Over 4 years, REBIF 132 g weekly was superior to REBIF 66 g weekly in reducing relapses and although this difference did not achieve statistical significance (p= 0.069), neither was the study powered to demonstrate a significant difference between two active treatment arms. REBIF 132 g weekly reduced the time to onset of progression of disability by 18 months compared to placebo crossover patients. High dose REBIF also reduced the number of EDSS 1-point changes made by a patient compared to placebo and compared to REBIF 66 g weekly. Both doses strongly diminished the MRI active lesion development and the accumulation of lesion burden over time compared to placebo. REBIF 132 g weekly was significantly more effective on MRI outcomes than REBIF 66 g weekly. These data demonstrate a continued benefit of REBIF therapy up to 4 years and provide further evidence of a dose-effect relationship in MS. Whereas after two years of therapy, there had been a consistent trend in favour of the high dose which was statistically significant for MRI active lesions, further observation to 4 years showed that these trends continued and for the majority of endpoints became statistically significant. Finally, patients treated early (study start) attained more benefit at 4 years than those delaying treatment until the start of year 3.

Exacerbation rate during Years 1-4: ITT (Intent to treat)
Time Period Estimated annual exacerbation rate
Placebo/ REBIF
REBIF 66 µg weekly
REBIF 132 µg weekly
Years 1-4 1.02 0.80 0.72
Treatment comparison p-value*
Years 1-4 REBIF 132 µg vs. placebo/REBIF
REBIF 66 µg vs. placebo/REBIF
REBIF 66 µg vs. REBIF 132 µg
*Poisson Regression model with effects for treatment and center and treatment by center interaction
Exacerbation count during years 1-2 and years 3-4 [all patients treated with placebo during years 1-2 (placebo switch patients)]
Time period Statistics Placebo/REBIF
66 µg weekly
132 µg weekly (n=87)
Years 1-2 Mean (SD)
2.60 (2.11)
(0.00, 10.00)
2.57 (1.99)
(0.00, 8.00)
Years 3-4 Mean (SD)
1.21 (1.55)
(0.00, 9.00)
1.23 (1.24)
(0.00, 6.00)
Change from Years 1-2 to Years 3-4 Mean (SD)
-1.39 (2.47)
(-10.00, 9.00)
-1.34 (1.85)
(-6.00, 2.00)
*p-value from Wilcoxon Signed-Rank test
Proportion of exacerbation-free patients at the end of year 4: ITT
Time Period Number and proportion of exacerbation-free patients
Placebo/ REBIF
n/N* (%)
66 µg weekly
n/N* (%)
132 µg weekly
n/N* (%)
Year 4 12/180 (6.67) 26/181 (14.36) 34/179 (18.99)
Treatment comparison p-value#
Year 4 REBIF 132 µg vs. placebo/ REBIF
REBIF 66 µg vs. placebo/ REBIF
REBIF 66 µg vs. REBIF 132 µg
* Exclude patients lost to follow-up without any exacerbation count
# p-value is from a logistic regression model with effects for treatment and center.
Time to first exacerbation (from 2 year database)
Placebo REBIF p-value
Efficacy parameters 66 μg/
132 μg/
66 μg/wk
vs Placebo
132 μg/wk
vs Placebo
Median time to first exacerbation (months) 4.5 7.6 9.6 0.0008 <0.0001
Time to second exacerbation (from 4 year database) and proportion with second relapses: ITT years 1-4
Time to second
REBIF 66 µg
132 µg
weekly n=184
Years 1-4 First quartile in days
Median in days
216 (7.1)

449 (14.8)
329 (10.8)

702 (23.1)
359 (11.8)

965 (31.7)
    Treatment comparison p-value#
Years 1-4   REBIF 132 µg vs. placebo
REBIF 66 µg vs. placebo
REBIF 132 µg vs. REBIF 66 µg
The first quartile and median time to second exacerbation are Kaplan-Meier estimates.
# p-value is from a Cox proportional hazards model with effects for treatment and center.

Time to progression for the ITT group shows that REBIF 132 µg weekly compared to placebo/treatment has a significant prolongation of the time to progression (p=0.047). This prolongation is 18 months for REBIF 132 µg weekly and 12 months for REBIF 66 µg weekly. There was no significant difference between the 132 µg/week dose and the 66 µg/week dose in the time to confirmed progression (p=0.333). Only the 132 µg/week dose was effective at reducing the time to confirmed EDSS progression in the ITT analysis. The time to first confirmed progression did not differ significantly between the 66 µg/week dose and the placebo crossover ITT group (p=0.289).

Proportion of progression-free patients at the end of Year 4: ITT
  Number and proportion of progression free patients
Time Period Placebo/REBIF
n/N (%)
REBIF 66 µg weekly
n/N (%)
REBIF 132 µg weekly
n/N (%)
Year 4 74/161 (46%) 88/173 (51%) 92/164 (56%)
  Treatment comparison p-value#
Year 4 REBIF 132 µg vs. placebo/REBIF
REBIF 66 µg vs. placebo/REBIF
REBIF 132 µg vs. REBIF 66 µg
Excludes patients lost to follow-up without any confirmed progression.
* p-value is from a logistic regression model with effects for treatment and center.
Number of confirmed EDSS changes during Years 1-4: ITT
Estimated confirmed annual progression rate *
Time Period Placebo/REBIF
REBIF 66 µg weekly
REBIF 32 µg weekly
Years 1-4 0.24 0.22 0.17
  Treatment comparison p-value#
Years 1- 4 REBIF 132 µg vs. placebo/REBIF
REBIF 66 µg vs. placebo/REBIF
REBIF 132 µg vs. REBIF 66 µg

Effect on MRI scans in multiple sclerosis

The MRI data show a highly significant effect of interferon therapy on BOD (burden of disease) and MRI activity measures, a highly significant dose effect on both BOD and MRI activity measures for patients treated with 132 µg weekly vs. 66 µg weekly after 4 years (p=0.009 and p<0.0001 respectively), an overall net reduction in BOD of 6.2% over 4 years in patients treated with 132 µg weekly, and that patients originally treated with the high dose of REBIF retain an overall significant benefit on BOD and activity measures compared to patients treated with placebo followed by 132 µg weekly for two years (p=0.003).

Percent change in burden of disease during Years 1-4: 4-treatment groups
Statistics Placebo/REBIF
66 µg weekly
132 µg weekly
REBIF 66 Ојg/
REBIF 132 Ојg/
Years 1-4 N
Mean (SD)
16.3 (31.0)
(-24.9, 151.5)
13.0 (31.0)
(-31.7, 124.6)
20.4 (71.3)
(-64.1, 351.0)
2.4 (34.5)
(-53.1, 188.1)
Treatment comparison p-value*
Years 1-4 REBIF
В 132 µ g vs. placebo/REBIF 132 µg
В  REBIF66 µg vs. placebo/REBIF 66 µg
REBIF132 µg vs. REBIF 66 µg
* p-value from an ANCOVA on ranks with effects for treatment and center adjusting for baseline burden of disease
Mean Number of T2 Active Lesions per Patient per Scan During Years 1-4 and 3-4: 4-Treatment Groups
Time Period Statistics Treatment Group
22 µg tiw
44 µg tiw
22 µg tiw
44 µg tiw
Years 1-4 N
Mean (SD)
4.0 (4.9)
(0.0, 26.5)
4.0 (4.0)
(0.0, 19.0)
2.6 (4.0)
(0.0, 22.3)
1.5 (3.3)
(0.0, 27.5)
Years 3-4 n
Mean (SD)
2.0 (3.3)
(0.0, 19.5)
1.8 (2.8)
(0.0, 12.0)
2.1 (3.5)
(0.0, 19.0)
1.2 (3.3)
(0.0, 23.5)
Time Period Treatment Comparison p-value(a)
Years 1-4 REBIF 44 µg tiw vs Placebo/ REBIF 44 µg tiw
REBIF 22 µg tiw vs Placebo/ REBIF 22 µg tiw
REBIF 44 µg tiw vs REBIF 22 µg tiw
< 0.0001
Years 3-4 REBIF 44 µg tiw vs Placebo/REBIF 44 µg tiw
REBIF 22 µg tiw vs Placebo/REBIF 22 µg tiw
REBIF 44 µg tiw vs REBIF 22 µg tiw
(a) p-value from and ANOVA on ranks with effects for treatment and center

Requirement for steroids

During the first two years, the proportion of patients requiring steroids for MS (excluding non-MS indications) was higher in the placebo group (more than 50%) than in either of the 2 REBIF groups (around 40% in each group). For patients on therapy for 4 years, the majority (76.4%) of steroid courses were for MS indications and over 90% of MS-related courses were for the treatment of exacerbations. Comparison of the rate of steroid use for actively treated patients over years 1-4 indicates a significantly lower rate in the 132 µg weekly group compared with the 66 µg weekly group (p = 0.032), providing supportive evidence of a dose-effect relationship for interferon therapy in MS.

Hospitalization for multiple sclerosis

During the first two years, the observed mean number of hospitalizations for MS in the REBIF 66 and 132 µg weekly groups represented reductions of 21% and 48%, respectively, from that in the placebo group. The number of hospitalizations per patient was 0.48 for placebo, 0.38 for 22µg tiw and 0.25 for 44 µg tiw. Only the difference between 44 µg tiw and placebo was statistically significant (p=0.038). After four years on study, comparison of the hospitalization rates was performed on only the two groups receiving active therapy during years 1-4. It revealed no significant difference between groups with a mean value of 0.2 (median = 0) and 0.1(median = 0) hospitalizations/patient/year for 66 and 132 µg groups, respectively. The lack of significant difference could in part be due to the low number of events overall even though the rate of 66 µg is double that of 132 µg.

Study GF7999 ( OWIMS: Once Weekly Interferon beta-1a for Multiple Sclerosis)

A total of 293 patients diagnosed with clinically definite or laboratory-supported relapsing MS with at least a one-year history, one or more exacerbations in the previous two years, 3 or more lesions on MRI at the pre-study scan, and an EDSS between 0 and 5.0 were enrolled and randomized to the 3 treatments (placebo, 22 µg REBIF, or 44 µg REBIF) in a ratio of 1:1:1. The patients were treated once weekly by subcutaneous injection. About 92% of patients completed 48 weeks, and very few patients withdrew from the study due to adverse events.

MRI as a measure of MS activity was evaluated in two ways: number of active lesions on T2-weighted and T1-weighted gadolinium enhanced MRI scans at Weeks 4, 8, 12, 16, 20 and 24 during treatment (and compared to baseline) and the burden of disease evaluated in all patients using the T2-weighted sequence at the same time points. Further T2-weighted MRIs were conducted at Weeks 48 and 96.

MRI Disease Activity

A non-significant decrease compared with placebo in combined active lesions per patient per scan was noted for the 22 µg QW dose (29.6%), and a modest yet significant reduction was apparent with the 44 µg QW dose (53.5%). A dose-effect was also noted in other MRI parameters: the percentage of MRI scans showing combined active lesions was 50%, 45% and 33% for placebo, REBIF 22 µg QW and REBIF 44 µg QW (not statistically significant). Only the highest dose of REBIF was associated with a significant reduction in the proportion of active scans (p=0.02), T2 active lesions alone and T1-Gd enhancing lesions alone (p<0.01) as compared to placebo.

MRI Disease Burden

Over 1 year of treatment, the change from baseline in burden of disease (total PD/T2 lesion area) differed significantly between both active treatment groups and placebo. Burden of disease increased from baseline in the placebo groups and decreased in the active treatment groups, (decreased by 2.0% and 1.4% for REBIF 22 µg and 44 µg QW, respectively, and no statistical difference was seen between the two groups).

Exacerbation Frequency

No reduction was evident with the 22 µg QW dose, and a 19% reduction was seen with the 44 µg QW dose, a difference that did not reach statistical significance (p=0.21), although the study was not powered for this outcome.


While some modest MRI effect was seen, no significant clinical benefit was seen over the one-year study duration. This study suggests that once weekly administration at doses of 22 or 44 µg does not provide significant benefit in established RRMS.

Study GF6954 SPECTRIMS: Secondary Progressive Efficacy Clinical Trial of Recombinant Interferon beta-1a (Serono) in Multiple Sclerosis)

GF6954 was a large randomized, double-blind, placebo-controlled three-year study performed to examine the effects of REBIF on key outcome parameters in a patient population with more advanced multiple sclerosis disease.

GF6954 was conducted in 22 centres in Europe, Canada, and Australia. A total of 618 patients (229 men and 389 women) aged 18-55 years with secondary progressive MS (EDSS 3-6.5) were randomized to receive REBIF 66 µg weekly (22 µg, 3x/week), 132 µg weekly (44 µg, 3x/week) or matching placebo as SC injections for 3 years. To reduce the occurrence of anticipated side effects, the dose was increased gradually: 20% of the assigned dose was given for two to four weeks, then 50% for two to four weeks, and the full dose thereafter.

The primary efficacy endpoint was the effect of treatment on the deterioration of disability. The deterioration of disability was prospectively defined as the time to progression in disability by at least 1.0 point on the EDSS, or a deterioration of 0.5 point if the baseline EDSS was ≥ 5.5, confirmed at two consecutive visits three months apart. Secondary outcome measures included relapse count, MS lesion activity measures on MRI and the change in total MRI lesion burden. Several tertiary outcome measures were also evaluated.

A total of 571 patients (92.4%) completed the 3-year study, with 96.5% of all possible data collected. The proportions of patients completing were similar in the placebo (90.7%), REBIF 66 µg (93.3%), and REBIF 132 µg (93.1%) groups. Of the 112 patients who discontinued prematurely, only 47 (7.6% of the overall population) were lost to follow-up. All analyses were based on intent-to-treat principles.

Clinical endpoints

The primary outcome measure was time to confirmed progression in disability, with the main comparison being between REBIF 132 μg tiw and placebo. Although a trend in favour of therapy was noted for the primary outcome, this difference was not statistically significant (p=0.146). An unexpected treatment by sex interaction was noted (p=0.035) which clouds interpretation.

The differential effect of treatment, based on whether or not patients had relapses during the 2 years before entry to the study, was also examined. After the sex-treatment interaction was identified, Serono investigated other possible baseline factors that could have possibly been related to the sex-treatment interaction. As part of this investigation, a number of clinically relevant baseline disease and demographic factors were each investigated in order to see if the sex-treatment interaction remained in the presence of these factors. As part of this process, it was noted that the number of relapses in the two years prior to the study also showed an interaction with treatment. The effect of treatment (both groups combined) on time to progression was analysed separately for “relapsing” and “non-relapsing” patients. This analysis indicated that the benefit for the combined treatment group was greater for relapsing patients (n=293) as opposed to non-relapsing patients (n=325). The hazard ratio for progression was 0.74 in the relapsing patients (p=0.055), while the hazard ratio was 1.01 in the non-relapsing patients (p=0.934). The corresponding odds ratios for proportion progressing in the treated relapsing and non-relapsing patients were 0.52 (p=0.027) and 1.07 (p =0.802), respectively.

Secondary endpoints

The three secondary endpoints were exacerbation count per patient, MRI activity and burden of disease.

Secondary endpoints results
Placebo REBIF
66 µg
132 µg
p value
66 µg vs.
p value
132 µg vs.
Exacerbation count per
patient at 3 years
2.05 ± 2.14 1.44 ± 1.63 1.46 ± 1.68 <0.001 <0.001
Relapse Rate (number
per year)
0.71 0.50 0.50 <0.001 <0.001
T2 Active lesions per
patient per scan (median)
0.67 0.20 0.17 <0.0001 <0.0001
T2 New lesions per
patient per scan (median)
0.33 0.17 0.00 <0.0001 <0.0001
T2 Newly enlarging
lesions per patient per
scan (median)
0.17 0.00 0.00 <0.0001 <0.0001
Mean % T2 active scans 46% 28% 24% <0.001 <0.001
% patients with no T2
active scans during
24% 36% 41% <0.001 <0.001
% Change in BOD
10 -0.5 -1.3 <0.001 <0.001

Both doses of REBIF conferred significant benefits, reducing the relapse rate by approximately 30% (p<0.001), reducing T2 activity by 70-75% (p<0.001), and the percentage change in BOD increased by 10% in the placebo group while decreasing by 1.3% and 0.5% in the low and high dose groups respectively (p<0.001 for both doses compared to placebo).

Allied to the T2 active lesion counts were significant effects of treatment on the proportion of active scans (66% reduction, p<0.001) and the proportion of patients who did not have any active lesions on their scans during the study (71% increase, p<0.001). The comparison of relapsing vs. non-relapsing patients revealed differences in both baseline MR characteristics and on-study behaviour and treatment response.

For the pre-study relapsing group of patients, treatment was more effective on the secondary outcome measures than for the non-relapsing sub-group, as occurred for the primary endpoint.

Summary of on-study behaviour of Relapsing vs. Non-relapsing patients
  Relapsing pre-study Non-relapsing pre-study

Dose of REBIF

132 µg 66 µg Placebo 132 µg 66 µg Placebo

Total number of patients per group

98 97 98 106 112 107

% progressing at the end of the study

59 56 70 58 63 61

Relapse rate (number per year)

0.67*** 0.57*** 1.08 0.36 0.43 0.39

T2 activity (median)

0.17*** 0.17*** 1.17 0.17* 0.20 0.33

% Change in BOD (median)

-1.3*** -1.5*** 11.8 -1.4*** 1.2 8.4
***: p<0.001, **: p<0.01, *: p<0.05 compared with placebo

Tertiary endpoints

Other relapse related outcome measures including time to first relapse (p=0.032), time between first and second relapse (p=0.002), relapse severity (p=0.049), need for steroid treatment (p=0.005) and need for hospitalisation (p=0.005), were all favourably affected by REBIF 132 µg treatment. The only relapse related measure which was not significantly affected by 132 µg therapy was relapse duration.

Composite Score

In a disorder such as MS, there are often multiple outcomes that may measure different impacts of the disease. These measures may be independent of one another but each may also be important to the overall benefit to the patient. A statistical method exists to combine these measures in one composite score. The value of this measure is that if all outcomes are favourably affected, a strong result is seen while if there are some outcomes with good effect and others without, the composite score will not show a treatment effect. In this study the five outcomes that were combined were time to progression, relapse count, T2 activity, change in BOD and IDSS (Integrated Disability Status Score). The composite score of these outcomes showed a highly significant result (p<0.001) in favour of REBIF at both doses.

Study GF7480 ( ETOMS: Early Treatment of Multiple Sclerosis)

A total of 309 patients with clinically probable or laboratory supported definite MS were randomized in this clinical trial to receive either 22 μg of REBIF once a week by S.C. injections or matching placebo for 2 years. Patients were to have their first MS attack in the 3 months preceding study entry and have MRI scan strongly suggestive of MS. About 78% of these patients received the allocated treatment during the 2-year study period and 90% remained on study until the end of 2 years. Over 85% of patients stopping blinded study treatment did so after having their second MS attack on study. Very few patients withdrew due to adverse events.

The treatment efficacy was determined by comparing the rate of patients converting to clinically definite MS (CDMS) in the active arm versus placebo. MRI as a measure of disease activity was evaluated by the number of new T2 lesions and the proportion of patients without MRI active scans.

Conversion to CDMS

A significant reduction in the proportion of patients converting to CDMS was observed in the treated group as compared to placebo (34% versus 45% respectively; p=0.047). The time to the second relapse increased significantly from 252 days in patients treated with placebo to 569 days for patients treated with REBIF (p=0.034). The annual relapse rate was significantly lower in the REBIF group (0.33) as compared to the placebo group (0.43) with a p value of 0.045.

MRI disease measures

A significant decrease compared with placebo in the number of new T2 lesions was observed in patients treated with REBIF 22 µg once a week (median 2.0 versus 3.0 respectively; p<0.001). The proportion of patients with no MRI active scan was significantly higher in the REBIF group (16%) than in the placebo group (6%) with a significant statistical difference (p=0.005). No difference between the study groups was observed for T1 active lesions. The total T2 lesion volume as compared to the baseline value increased of 8.8% in the placebo group while a decrease of 13% was observed in patients treated with REBIF 22 µg once a week; the difference being statistically significant (p=0.002).


This study demonstrated that 22 μg of REBIF injected once weekly significantly reduced the risk of a second relapse leading to the conversion to CDMS in patients with a first episode highly suggestive of MS. The clinical benefit was confirmed by a significant impact on MRI lesion activity and accumulation of disease burden.

Study 21125 (EVIDENCE: Evidence for Interferon Dose Effect: European-North American Comparative Efficacy Study)

This was an open-label, randomized, multicenter, parallel-group comparator study. Patients eligible for inclusion were clinically definite or laboratory-supported definite relapsing-remitting multiple sclerosis patients, with EDSS scores ranging from 0 to 5.5, clinically active disease defined as two or more relapses in the previous two years, and had no previous treatment with interferon. Patients were randomized to treatment with either IFN beta-1a 44 µg tiw given by s.c. injection (REBIF) or IFN beta-1a 30 µg qw given by i.m. injection (AVONEX) for a duration of 48 weeks. Neurologists blinded to treatment performed clinical evaluations, and assessors blinded to treatment performed central MRI evaluations. The primary efficacy endpoint was the proportion of patients who remained exacerbation-free at 24 weeks. The principal secondary endpoint was the mean number of combined unique (CU) active MRI lesions per patient per scan defined as T1 or T2 active.

Patient population

Of the 677 patients randomized, 339 patients received REBIF 44 µg SC three times a week (tiw) and 338 patients were assigned to AVONEX 30 µg IM once a week (qw). One patient randomized to the AVONEX group did not receive treatment. No statistically significant differences were noted in demographics between the randomized groups. A high percentage of both REBIF and AVONEX patients completed 24 weeks (95.0% and 96.4% respectively) and 48 weeks (92.6% and 93.7% respectively) of treatment.

Efficacy results

Patients treated with REBIF were significantly more likely to remain relapse free after 24 weeks than patients treated with AVONEX (74.9% vs. 63.3% respectively). The odds ratio adjusted for center was=1.9, p<0.001. Thirty-two percent fewer patients on REBIF relative to AVONEX experienced a new relapse during this 24-week period. After 48 weeks, a significantly higher proportion of REBIF treated patients remained relapse free as compared to the AVONEX treated patients (62% vs 52%, respectively, p=0.009; adjusted odds ratio=1.5, p=0.009).

Time to first relapse was prolonged over the course of the 48 week study for patients treated with REBIF, HR=0.7, 95% CI 0.55-0.88, p=0.003.

The absolute count of relapses by severity was less for REBIF treated patients compared to AVONEX treated patients for each level of severity. The rate of steroid use to treat relapses for REBIF patients was approximately half that of AVONEX patients during the 24-week period (p=0.004).

The MRI outcome measures provided strong support for the clinical findings There was approximately a one-third relative reduction in MRI CU lesion activity for REBIF compared to AVONEX over the 24-week treatment period (0.8 vs 1.2 respectively, p<0.001). Other MRI activity measures showed similar benefits favoring REBIF over 24 and 48 weeks (p<0.001). The mean number of T1 enhancing and T2 active lesions per patient per scan was significantly reduced in the REBIF group (p<0.001). In addition, the mean proportion of patients with no active scans in the REBIF treated group was significantly higher for CU, T2 and T1 lesion assessments over 24 and 48 weeks (CU, T2, and T1, p<0.001).

Safety results

Treatment was generally well tolerated in both treatment groups, with the majority of adverse events in both groups considered mild. The most common adverse events experienced in this study were well described consequences of IFN administration. They included flu- like symptoms (42% on REBIF and 49% on AVONEX; p = 0.089), injections site disorders (83% for REBIF and 28% for AVONEX; p<0.001), hepatic dysfunction (18% on REBIF and 10% on AVONEX; p=0.002), and leukopenia (6% on REBIF and <1% on AVONEX; p<0.05).

There were 21 patients that experienced serious adverse events in the REBIF group (6%) and 18 in the AVONEX group (5%), and 9 of the events were considered related to treatment. Treatment discontinuation because of adverse events occurred in 16 of the REBIF patients (4.7%) and 14 of the AVONEX patients (4.2%).


This randomized controlled study demonstrated a greater efficacy of REBIF compared with AVONEX on both relapse and MRI outcomes over 48 weeks. Despite considerable differences in dosing regimens, the overall safety profiles of the treatments were similar with differences noted only in the incidence of specific safety events, and there was no dose-limiting toxicity.

Study 25632 (REBIF HSA-free Formulation)

This was a multi-national, 96-week, single-arm, open-label study, with patients treated with the HSA-free Formulation of REBIF three times a week. The primary objective of the study was to compare the immunogenicity of the FBS-free/HSA-free interferon-beta-1a (REBIF) formulation (RNF) to historical data. Patients with a relapsing form of MS according to the McDonald criteria, an EDSS<6.0 and no prior interferon beta therapy were enrolled.

The data from study 25632 (“REBIF HSA-free Formulation Cohort”) is compared to historical data from the 44 µg tiw treatment arms of studies 6789 (PRISMS), 6954 (SPECTRIMS) and 21125 (EVIDENCE) (collectively referred to as the “Historical Cohort”). These studies were selected for comparison as they were pivotal controlled studies in patients with MS and included a treatment arm with identical dosing and route of administration. In study 21125, REBIF was also supplied in an identical format, pre -filled syringes. Studies 6789 and 21125 were conducted only in a relapsing MS population and study 6954 was conducted in an SPMS (with or without superimposed relapses) population.

Subject Disposition

A total of 282 subjects were screened for trial entry, of whom 260 were enrolled between 25 Jan 2005 and 6 Jun 2005. All 260 enrolled subjects received trial medication and were included in the REBIF HSA-free Formulation Cohort Safety Population; one had no post-baseline NAb data and was therefore excluded from the ITT Population. Considering the REBIF HSA-free Formulation Cohort Safety Population, 207 subjects (79.6%) completed treatment and 224 subjects (86.2%) completed the trial. Adverse events were the most frequent reason for early discontinuation.

Demographics and Baseline Characteristics

The median age of the 260 enrolled subjects in the REBIF HSA-free Formulation Cohort was 34 (range: 18 to 58), and the majority of the subjects (71.5%) were female, which is consistent with the MS population. Almost all of the subjects were White (253/260 [97.3%]) . The majority of subjects had RRMS (97.3%), while 6 subjects had SPMS with superimposed relapses and one subject had PPMS. Duration of MS varied across the subjects with a median of 5.45 years (range: 0.2 to 33.2).

Seven hundred and twenty-seven (727) subjects treated with interferon beta-1a 44 µg tiw were included in the Historical Cohort (Studies 6789, 6954 and 21125). The median age of subjects in the REBIF HSA-free Formulation Cohort was similar compared to Study 6789 and lower compared to Study 6954 (this is expected as this was an SPMS population) and Study 21125. Sex and race were similar between the REBIF HSA-free Formulation and Historical Cohorts. Studies 6789 (n=184) and 21125 (n=339) enrolled subjects with RRMS (median EDSS scores: 2.48 and 2.34, respectively). Study 6954 (n=204) enrolled subjects with SPMS (median EDSS scores: 5.35).

Primary Endpoint Analysis

At Week 96 or last assessment, 45 subjects (17.4%) were Nab positive . Immunogenicity results were comparable with historical REBIF studies; the proportion of subjects NAb-free at Week 96 was similar or better than that observed in previous trials.

Safety Results

No new or unexpected safety concerns were identified during 96 weeks of study 25632. Adverse events reported over 96 weeks were consistent with those reported by the Historical Cohort.

Overall, 247 of the 260 subjects (95.0%) in the REBIF HSA-free Formulation Cohort experienced 1979 AEs. The system organ classes with the largest proportion of treatment emergent AEs were “general disorders and administration site conditions” (223 subjects, 611 events) and “nervous system disorders” (123 subjects, 316 events) . The majority of adverse events in the REBIF HSA-free Formulation Cohort were mild (86.5%) or moderate (60.8%) in severity, and the majority of AEs were classified as possibly (70.8%) or probably related to treatment (52.7%).

Fifteen of the 260 subjects (15/260 [5.8%]) in the REBIF HSA-free Formulation Cohort experienced 20 SAEs. One event reported as serious in more than one subject was depression (3 events in 3 subjects). The system organ classes with the largest proportion of SAEs were injury, poisoning and procedural complications (5 events in 5 subjects), psychiatric disorders (4 events in 4 subjects), reproductive system and breast disorders (3 events in 3 subjects) and gastrointestinal disorders (2 events in 2 subjects); for other SOCs, serious events were reported in no more than one subject. Five of the 20 SAEs experienced by the REBIF HSA-free Formulation Cohort were considered possibly or probably related, and 15 events were considered unlikely or unrelated to treatment. No deaths were reported during this trial.

Thirty-one subjects (11.9%) discontinued treatment permanently because of adverse events, citing a total of 52 events as reasons for treatment discontinuation. A further 3 subjects became pregnant during the trial and consequently stopped treatment (one underwent an induced abortion and the other two gave birth to healthy children). Influenza-like symptoms and laboratory abnormalities known to be associated with interferon-beta treatment (elevations in liver function tests and cytopenia) were prominent among reasons for discontinuation. Two subjects discontinued treatment because of local injection site symptoms.

To facilitate the analysis of the safety data, adverse events commonly associated with IFN- were prospectively classified into a series of pre-specified AE groups of related MedDRA preferred terms which best represented the AE of interest. These pre-specified AE groups were defined as “injection site reactions”, “flu-like syndrome”, “cytopenias”, “hepatic disorders”, “thyroid disorders”, “depression and suicidal ideation”, “skin rashes” and “hypersensitivity reactions”. For “hepatic disorders” the Standard MedDRA Query was used adapted to the study population. The pre-specified AE group “flu-like syndrome” included all reports of “influenza-like illness” as well as at least two pre-specified preferred terms representing typical flu-like symptoms occurring concomitantly, i.e. within a 48-hour interval. The frequencies of these pre-specified AE groups for the REBIF HSA -free Formulation Cohort were compared to those reported by the Historical Cohort during 96 weeks of treatment.

Pre-specified Treatment Emergent Adverse Events reported up to Week 96 or Month 24 for both the REBIF HSA-free Formulation Cohort and the Historical Cohort
Pre-specified group 25632
44 µg TIW
n (%)
44 µg TIW
n (%)
44 µg TIW
n (%)
44 µg TIW
n (%)
Cytopenia 35 (13.5) 71 (38.6) 81 (39.7) 44 (13.0)
Depression and Suicidal Ideation 17 (6.5) 55 (29.9) 74 (36.3) 77 (22.7)
Flu Like Syndrome 186 (71.5) 127 (69.0) 113 (55.4) 166 (49.0)
Hepatic Disorders 37 (14.2) 70(38.0) 67 (32.8) 63 (18.6)
Hypersensitivity Reactions 15 (5.8) 22 (12.0) 19 (9.3) 19 (5.6)
Injection Site Reaction (ISR) 80 (30.8) 170 (92.4) 176 (86.3) 291 (85.8)
Skin Rashes 16 (6.2) 44(23.9) 52 (25.5) 56 (16.5)
Thyroid Disorders 11 (4.2) 16 (8.7) 10 (4.9) 25 (7.4)

Injection tolerability is a key factor in treatment compliance, especially for a product, which must be administered chronically, where injection site reactions are a frequent cause of treatment discontinuation. The development of the REBIF HSA-free Formulation has focused on improving injection site tolerance through targeted formulation enhancements. A near 3-fold improvement in local tolerability was observed following administration of the new formulation when compared to historical data. After 96 weeks of treatment, the REBIF HSA-free Formulation Cohort experienced a much lower rate for the pre-specified AE group “injection site reactions” (30.8%) than the Historical Cohort (85.8% to 92.4% ).

Overall, 226 subjects (86.9%) in the REBIF HSA- free Formulation Cohort experienced at least one “pre-specified” adverse event. Events related to the flu-like syndrome were reported in 71.5% of REBIF HSA-free Formulation subjects and in 69.0%, 55.4% and 49.0% of subjects in protocols 6789, 6954 and 21125 respectively. Local injection site reactions were 30.8% of subjects in the REBIF Cohort compared with 85.8% to 92.4% in the historical trials. Events related to depression and suicidal ideation affected 6.5% of REBIF HSA-free Formulation subjects compared with 22.7% to 36.3% in the historical trials. Rates of cytopenia and hepatic disorders in the REBIF New HSA-free Formulation Cohort were 13.5% for REBIF HSA-free Formulation, 13.0% for 21125, 38.6% for 6789 and 39.7% for 6954; hepatic disorders: 14.2% for REBIF HSA-free Formulation, 18.6% for 21125, 38.0% for 6789 and 32.8% for 6954. Skin rashes were 6.2% in the REBIF HSA-free Formulation group and 16.5% - 25.5% in historical populations. Rates of hypersensitivity reactions and thyroid disorders observed in the REBIF HSA-free Formulation group were similar to those seen in the previous trials (hypersensitivity reactions: 5.8% for REBIF HSA-free Formulation and 5.6% to 12.0% in historical groups; thyroid disorders: 4.2% for REBIF HSA-free Formulation and 4.9% to 8.7% in historical trials).

Most of the laboratory parameters remained constant and within normal limits during the 96 weeks of treatment. The distribution of the haematology and biochemistry worst post-baseline CTCAE grades shift analyses from baseline to Week 96 were similar between the REBIF HSA-free Formulation Cohort and the Historical Cohort. The majority of worst post-baseline CTCAE grades for haematology and biochemistry parameters were Grade 0 or 1, but a low frequency of grade 2 to 4 haematological toxicity, principally neutropenia, and hepatic transaminase elevation was observed, comparable to that of the Historical Cohort.


Safety data generated during 96 weeks of treatment in study 25632 indicate that the new HSA-free formulation of IFN- -1a possesses a safety profile qualitatively similar to that of the previously marketed HSA-containing REBIF formulation, represented by the Historical Cohort.

Study 27025 (REFLEX: REBIF Flexible Dosing in Early Multiple Sclerosis)

One randomized, double-blind, placebo-controlled clinical trial with REBIF HSA-free formulation was performed in patients with a single clinical demyelinating event at high risk of conversion to multiple sclerosis (MS) over 24 month treatment period. Subjects eligible for the trial were 18 to 50 years old with an EDSS of ≤ 5.0, presented with a single, first clinical event suggestive of MS within 60 days after the onset and at least two clinically silent lesions on the T2-weighted MRI scan, with a size of at least 3 mm, of which at least one was required to be ovoid or periventricular or infratentorial. Any disease other than multiple sclerosis that could better explain signs and symptoms of the patient had to be excluded. Patients were randomized (1:1:1) to either REBIF 44 mcg given subcutaneously three times per week (tiw) (n=171), REBIF 44 mcg once weekly (ow) (n=175), or placebo (n=171). Upon conversion to clinically definite multiple sclerosis (CDMS), patients were re-titrated to the recommended dose of REBIF 44 mcg tiw in an open label manner, while maintaining blinding as to initial randomization.

Efficacy Results

The primary efficacy endpoint (Time to conversion to McDonald MS), the main secondary clinical endpoint (Time to conversion to CDMS) and the MRI-based efficacy endpoint (Mean Number of CUA lesions) were tested by primary analyses using a 2-sided log rank test at the 0.05 significance level stratified by the randomization stratification factors (age group, steroid use, presence/absence of Gd-enhancing lesions and classification of first clinical demyelinating event). A hierarchical approach based on the significance of the relevant confirmatory test was applied, comparing RNF 44 mcg tiw vs. Placebo for:

  1. Time to conversion to McDonald MS;
  2. Time to conversion to CDMS;
  3. Mean number of combined unique active MRI lesions per subject per scan. The secondary analysis for both endpoints was the estimate of the treatment effect estimated by hazard ratios using an adjusted Cox’s proportional hazards model including treatment and the randomization stratification factors as covariates. The main MRI-based secondary endpoint was the mean number of CUA MRI lesions per subject per scan using a non-parametric analysis of variance (ANOVA) on ranks model including treatment and randomization stratification factors as covariates.
Primary Efficacy Endpoint: Time to Conversion to McDonald MS (2005 criteria)

A subject was considered to have converted to MS according to the 2005 McDonald criteria if, following the first clinical demyelinating event, there was evidence of dissemination in space and in time based on a clinical event or on clinical data and MRI.

Over 24 months, RNF 44 mcg tiw delayed the progression to McDonald from the first clinical event compared to Placebo. The risk reduction was 51% (HR = 0.49, 95% CI [0.38, 0.64]) for RNF 44 mcg tiw compared to Placebo (Log-rank test: p<0.001 ).

Based on KM estimates, the cumulative probability of conversion to McDonald MS over 24 months was 85.8% in the Placebo group compared to 62.5% in the RNF 44 mcg tiw. The median time for conversion to McDonald MS was 97 and 310 days in the Placebo and the RNF 44 mcg tiw groups, respectively.

Main Secondary Clinical Efficacy Endpoint: Time to Conversion to CDMS

Time to conversion to CDMS was defined by either a second attack or a 3-month sustained increase (≥ 1.5 points) in the EDSS score.

Over 24 months, RNF 44 mcg tiw delayed the progression to CDMS compared to Placebo. The risk reduction was 52% (HR = 0.48, 95% CI [0.31, 0.73]) for RNF 44 mcg tiw compared to Placebo.

Based on KM estimates, the probability of the development of CDMS over 2 years was 37.5% in the Placebo group compared to 20.6% in the RNF 44 mcg tiw. The median time was not reached.

Main MRI-based Efficacy Endpoint: Mean Number of CUA Lesions Per Subject Per Scan

CUA lesions per subject per scan provides the most comprehensive information on lesion activity in the brain of MS subjects by integrating both T2 weighted and post-Gd weighted T1 image information. At the end of the double-blind period, the mean number (SE) of CUA lesions was 0.50 ± 0.06 and 2.58 ± 0.30 for RNF 44 mcg tiw and Placebo groups, respectively. Rate ratio and 95% CI was 0.19 (0.14; 0.26) (p<0.001, non-parametric ANOVA).

Efficacy Results from Study 27025 up to 24 Month Period
Parameter Statistics Treatment Treatment
RNF 44
mcg tiw**
RNF 44 mcg
McDonald Conversion
Number of events 144 106  
KM Estimate (a) 85.8% 62.5%  
Median Time (days) 97 310  
Risk Reduction     51%
Hazard Ratio [95% CI] (b)     0.49 [0.38;0.64]
Log-rank p-value (c)     0.001
(a) Kaplan-Meier estimate of the cumulative probability of developing McDonald MS (or CDMS) over 2 years
(b) Multivariate Cox's proportional hazards model with treatment and randomization stratification factors as covariates
(c) Stratified Chi-square log-rank test controlling for randomization stratification factors

Detailed Pharmacology

Animal Pharmacology

Animal Pharmacodynamics

A study of the cardiovascular and respiratory effects of REBIF (Interferon beta-1a) has been carried out in a conventional anaesthetized, instrumented model in the rat. Bolus IV doses up to 11 μg/kg showed no effects on cardiac function, ECG, blood pressure or respiration.

REBIF has been tested in toxicology studies up to 3 months in duration in rats and up to 6 months in monkeys. No toxicities except for transient pyrexia were observed.

Acute and repeated dose toxicity studies in rat and cynomolgus monkey showing that doses up to 73 μg/kg IV or IM did not produce clinical signs of dysfunction of the nervous system, gastrointestinal tract and smooth muscle, or dysfunction of their physiological control. These acute experiments also showed that REBIF 73 μg/kg IV and IM caused transient pyrexia (in monkeys, this also occurred in the 13-week study at REBIF doses of 0.25-3.67 μg/kg IV).

Animal Pharmacokinetics

The single dose kinetics of REBIF has been examined in the rat and monkey to validate their use in toxicity tests as a model for man. The outcome of these studies is confirmed by the comparability of the findings with the results of single dose studies of other hIFN-betas, and the information gained from them about kinetics after multiple dosing. Absorption from an SC or IM site is rapid, the bioavailability is about 30-40% and some circulating IFN-beta persists up to 24 hours in the cynomolgus monkey dosed SC. Slight accumulation occurred after twice daily SC or IM dosing.

Human Pharmacology

The following studies are based on the original REBIF formulation (HSA formulation). This formulation is being replaced with the REBIF HSA-free Formulation described below (see Clinical Pharmacology Program with the HSA-Free Formulation of Interferon beta-1a).

Human Pharmacokinetics

In a randomized, double-blind, placebo-controlled, cross-over study, 12 healthy volunteers were injected with a single dose of 22 μg REBIF by the IV, IM or SC route. The pharmacokinetic analysis showed that 22 μg REBIF administered by the IV route follows a two-compartment model with a short distribution half- life of approximately 5 minutes and an elimination half-life of about 5 h, (similar results have also been reported for IFN-beta-1b). Following IM or SC administration, REBIF showed a rather flat plasma concentration/time curve, (similar to the data obtained in rats and monkeys), with an absolute bioavailability of about 15%.

The bioavailability of human interferon beta following single-dose subcutaneous and intramuscular administration of recombinant human interferon beta-1a was compared. The pharmacokinetic parameters showed a high intersubject variability, but intramuscular and subcutaneous routes of administration demonstrated equivalent bioavailability.

Human Pharmacodynamics

2'-5'- oligoadenylate synthetase is an enzyme shown to be produced in response to exposure to IFN both in vitro and in vivo. In the above mentioned randomized study, it was found to increase following REBIF administration, however, the mean peak elevation was independent of the route of administration. The increase in (2-5A) synthetase levels was maximal at 24 h (earlier samples were not collected) and levels were still significantly elevated 72 h after REBIF injection.

Previous work has shown these biomarkers to be of value in assessing the pharmacodynamics of interferons, but the relationship between serum IFN-beta concentration, measurable pharmacodynamic response and the mechanism(s) by which REBIF exerts therapeutic effects in multiple sclerosis remains essentially unknown.

Additional studies investigated the importance of increased frequency of administration. The results confirmed that more frequent administration (i.e., three times per week vs. once per week) elicits the optimal pharmacologic response.

Clinical Pharmacology Program with the HSA-free Formulation of Interferon beta-1a

Human Pharmacokinetics

The clinical pharmacology program compared the HSA- free Formulation of REBIF to the previously marketed HSA-containing formulation of REBIF at a dose of 44 µg interferon beta-1a. The biocomparability assessment that was performed as a secondary objective of the study was influenced by the high variability of the PK parameters. Standard bioequivalence criteria were not met for Cmax or AUClast.

The table below represents summary of the results of a non-compartmental analysis between the previously marketed formulation of REBIF and the current HSA-free formulation of REBIF, based on Study 25394 and 25827.

Summary of Pharmacokinetic Parameters for REBIF Formulations Non-compartmental Analysis of the Evaluable Population. Dose of 44 µg/kg

Tmax (h) (n=38)
Median 0.33 0.25
Range 0.033 - 168.00 0 0.167 - 0.50
Cmax (IU/mL) (n=38)
Mean ± SD1 11.8 ± 8.41 1 19.8 ± 12.26
Geometric Mean 1 10.22 1 17.10
Median 10.25 17.15
Median Range 3 3.8 - 53.0 6 6.6 - 71.0
AUCT (IU/mL*hr) (n=38)
Mean ± SD1 107.6 ± 248.1 1 109.0 ± 137.0
Geometric Mean 31.9 54.0
Median 31.35 47.2
Median Range 2 2.1 - 1300 2 2.63 - 676
Half-life (hr) (n=12)
Mean ± SD 1 12.78 ± 6.66 1 13.32 ± 11.32
Geometric Mean 1 10.85 9 9.80
Geometric CV (%) 7 72.8 1 104.46
Range 2 2.91 - 25.56 1 1.49 - 38.59

Special Tolerance Studies in Human

In an open-label study in patients with malignant diseases unresponsive to standard therapies, REBIF (Interferon beta-1a) was given as a bolus IV injection on day 1, followed one week later by daily subcutaneous injections for 28 consecutive days at the following dose levels: 5.5, 11, 22, 44, 66 or 88 μg/m2. Preliminary results indicate that the maximum tolerated dose is probably 44 μg/m2.


The following studies are based on the original REBIF formulation (HSA formulation).

Acute Toxicity

In formal single dose tests in the mouse and rat, REBIF (Interferon beta-1a) doses of 37 μg/kg and 73 μg/kg administered by intravenous or intramuscular route showed no effects during life or at autopsy.

In a similar experiment in cynomolgus monkeys, REBIF doses of 73 μg/kg IV or IM produced

only a 1-2 C rise in rectal temperature from 2 to 7 hours. No other effects were seen in the acute studies.

Repeated Dose Toxicity

All these experiments have been affected by the development of neutralizing antibodies against Interferon beta-1a (and the HSA carrier protein in the formulation).

In the rat, the principal findings were of local trauma at the sites of the repeated injections and of higher titre antibodies against HSA than against Interferon beta-1a by week 4, and increasing in incidence at week 13. The experiment using the IV route was marred by a number of accidental deaths mainly due to respiratory infection probably associated with tail (injection site) damage. Injection site lesions occurred in all groups, including the control group, and may have been possibly consequent on several factors, including needle trauma and a local allergic reaction to heterologous proteins (Interferon beta-1a and/or HSA) which predisposed to local infection with daily venipuncture. The infections spread then to the lungs (bacterial emboli). The studies in the cynomolgus monkeys showed brief pyrexia on day 1 after all IV doses (0.917 μg - 3.67 μg/kg), which was not present subsequently. The other findings were of anti-HSA and anti Interferon beta-1a antibodies appearing by week 4, and local trauma at the injection sites in all groups, including controls. No other findings were recorded.

Genetic Toxicity Testing

REBIF has been shown to be neither mutagenic nor clastogenic.

Reproduction Toxicity Testing

A teratology study in monkeys was performed showing that REBIF is not teratogenic. An increased risk of abortion has been attributed to the interferons, based on observations with interferon alpha and interferon beta-1b. No information is available on the effects of the interferon beta-1a on male fertility.

In addition, a single dose toxicity study in Cynomolgus monkeys and a local tolerability study in rabbits were conducted using the new formulation (HSA-free drug substance and HSA-free drug product, respectively). These studies did not reveal any additional toxicity concerns.