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Rebif, manufactured by Ares-Serono, is a form of beta interferon (interferon beta, IFN-b) used to modify the course of multiple sclerosis. While not a cure, Rebif has been shown in clinical trials to reduce the average relapse rate in people with the  relapsing-remitting multiple sclerosis (RRMS) form of the disease. That doesn't mean that it reduces the relapse rate for all the trial volunteers, just that averaged over the entire volunteer population, the relapse rate is reduced.

Rebif was licensed in Europe for use with RRMS in 1998 and approved by the US FDA in 2002. The gap in time between the two is explained by the protection given to the rival product, Avonex, by the orphan drug laws in the US.

Rebif is a form of beta interferon known as interferon beta-1a. It is identical to the naturally occurring protein found in the human body. Rebif is the same substance as Avonex but administered differently (22 mcg or 44 mcg, sub-cutaneously, 3 times a week as against 30 mcg, intra-muscularly, once a week for Avonex).

Here is a table of clinical trials of Rebif.
Efficacy of Rebif in Relapsing-Remitting Multiple Sclerosis
Trial Name Brief Description Results References
The IFNB Multiple Sclerosis Study Group The pivotal multi-centre phase III Rebif study published in 1993. 372 people with RRMS received either placebo, 1.6 MIU or 8 MIU of Rebif sub-cutaneously for 3 years. Relapse rates were reduced in the Rebif groups (placebo, 1.27; 1.6 MIU Rebif, 1.17; and for 8 MIU Rebif, 0.84). Burden of disease under MRI was reduced by 80%. Neurology 1993 Apr; 43(4) : 655-61

Neurology 1993 Apr; 43(4) : 662-7

Prevention of Relapses and Disability by Interferon beta-1a Subcutaneously in Multiple Sclerosis (PRISMS) Multi-centre phase III trial published in 1998. Of 560 people with EDSS scores of 0-5.0, 189 were given subcutaneous 22 mcg Rebif three times a week, 187 were given Rebif at 44 mcg and 187 were given a placebo for 2 years. Average relapse rates were 1.73 per year for the 44 mcg group, 1.82 per year for the 22 mcg group and 2.56 for placebo group. Time to first relapse was increased by 3 months for the 22 mcg group and 5 months for the 44 mcg group.  Lancet. 1998 Nov 7;
352(9139) : 1498-504
PRISMS-4: Long-term efficacy of Rebif in relapsing MS A two year extension to the original PRISMS study above. Years 3 and 4 were reported in 2001. Half the people taking the placebo in the original study were crossed over to 22 mcg and the other half to 44 mcg. Relapse rates were 0.72 for those on 44 mcg, 0.80 for those on 22 mcg and 1.02 for the crossover group. Time to sustained disability was 18 months greater in the 44 mcg group compared with the crossover. Burden of disease under MRI was greater in the crossover group. Neurology. 2001 Jun 26; 56(12) : 1620
Effect of early Rebif treatment on conversion to definite multiple sclerosis Phase III trial published in 2001. Of 308 people with a single neurological episode, half were given Rebif at 22 mcg sub-cutaneously once a week for 2 years and half received a placebo. 52 (34%) of people taking Rebif were subsequently diagnosed with clinically definite MS as opposed to 69 (45%) of the 154 people taking the placebo. ACP Journal Club. 2002 Jan-Feb; 136 : 21.

Lancet 2001 May 19; 357(9268) : 1576-82

Comparative trials involving Rebif
Trial Name Brief Description Results References
Evidence for Interferon Dose-Response: European-North American Comparative Efficacy (EVIDENCE) Multicentre, randomised, assessor-blinded trial. 677 patients with RRMS - 339 received Rebif, 44 mcg three times weekly and 338 received Avonex, 30 mcg once weekly for 48 weeks. After 24 weeks, 74.9% with Rebif remained relapse-free compared with 63.3% on Avonex. Rebif users had an average of 0.8 new lesions per scan while Avonex had an average of 1.2 new lesions per scan. Coyle PK et al - speakers' abstracts, AAN 54th Annual Meeting, April 2002

Sharief MK - speakers' abstracts, AAN 54th Annual Meeting, April 2002

Coyle PK. J Neurol Sci 2001;187 Suppl 1:S436

Efficacy of Rebif in Secondary Progressive Multiple Sclerosis
Trial Name Brief Description Results References
Secondary Progressive Efficacy Clinical Trial of Recombinant Interferon-beta-1a in MS (SPECTRIMS) Multi-centre phase III trial published in 2001. 618 people with SPMS received subcutaneous placebo or interferon beta-1a (Rebif), 22 or 44 mcg three times a week for 3 years. Rebif did NOT significantly affect disease progression although relapse rate was reduced from 0.71 per year with placebo to 0.50 per year with treatment and burden of disease under MRI was also reduced. Neurology 2001 Jun 12; 56(11) : 1496-504

Neurology 2001 Jun 12; 56(11) : 1505-13


More information about Avonex including comparative information between the various disease modifying treatments for multiple sclerosis can be found by following these links:
ABC treatments
interferon beta

Rebif links:
NMSS - Medications Commonly Used In MS - Rebif
Sigma Health - Rebif Information for Multiple Sclerosis

MS Glossary
All About Multiple Sclerosis