Avonex (interferon beta-1a) for multiple sclerosis
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What is Avonex for MS?
Avonex (interferon beta-1a) is an approved injectable medication that can help multiple sclerosis (MS) patients in three different ways: by slowing disability progression, lowering the frequency of relapses, and reducing brain lesions on MRI scans. The therapy was developed by Biogen and is approved in the U.S. and the EU, as well as in other countries worldwide.
Therapy Snapshot
| Brand name: | Avonex |
| Chemical name: | Interferon beta-1a |
| Usage: | Disease-modifying therapy for relapsing forms of MS |
| Administration: | Intramuscular injection |
How does Avonex work?
MS is caused by the body’s immune system erroneously attacking healthy parts of the nervous system. Interferon beta-1a, the active ingredient in Avonex, is a naturally occurring signaling protein that immune cells use to communicate with each other. But its levels are low in many MS patients.
The molecule, in particular, works to prevent excessive inflammation.
Avonex injections are thought to modulate immune activity, ultimately reducing the MS-driving immune attack on the nervous system. However, the exact mechanisms through which interferon beta-1a affects various parts of the immune system are still not completely understood.
Interferon beta-1a is also the active ingredient in Rebif and Plegridy, two other MS therapies.
Who can take Avonex?
The U.S. Food and Drug Administration approved Avonex in 1996 to treat adults with relapsing forms of MS, including relapsing-remitting MS (RRMS) and active secondary progressive MS (SPMS). Its indications in the U.S. were expanded in 2003 to include clinically isolated syndrome (CIS).
The European Commission, which regulates medicines in the EU, approved Avonex in 1997 for RRMS and active SPMS, and extended its use to CIS in 2003. The therapy is currently approved in more than 90 countries, according to Biogen.
Who should not take Avonex?
The medication is not recommended for people with a known allergy to interferon beta, albumin, or any other component in Avonex. If an allergic reaction occurs, treatment should be stopped.
How is Avonex administered?
Avonex is given via intramuscular injection, or injection directly into the muscle tissue, once a week. It is available in two forms:
- a single-dose prefilled syringe
- a single-dose autoinjector pen called the Avonex Pen
The recommended dosage of this therapy is 30 micrograms (mcg). However, the first doses can cause flu-like symptoms. Therefore, patients beginning the medication initially receive a lower 7.5 mcg dose on the first week, and gradually increase their dose over the next three weeks.
A titration kit called AVOSTARTGRIP is available for patients starting on Avonex. This includes three titration devices in different colors that are attached on top of a pre-filled syringe to ensure patients gradually increase their dose of Avonex over the first weeks. A white device is used to deliver one-quarter of a dose in the first week, followed by a yellow device that ensures patients receive half a dose on week 2. A purple device then is used in the third week to deliver three-quarters of a dose.
Avonex’s formulations are designed for one-time use only and should be administered in the upper, outer thigh or upper arm. Injection sites should be rotated to avoid injection site reactions. On the day of injection, premedication with over-the-counter analgesics (medicines to treat pain), or anti-fever medications, may help reduce the severity of flu-like symptoms.
The therapy can be administered at home, but the first injection should be performed under the guidance of a healthcare professional and patients should be instructed in the proper injection technique. Avonex should be taken from the refrigerator about 30 minutes before injection to reach room temperature.
| Administration | Intramuscular injection in upper, outer thigh or upper arm |
| Dosage | 30 mcg (7.5 mcg dose during the first week, with a gradual increase in dosage over the next three weeks) |
| Timing | Once a week |
Avonex in clinical trials
Avonex’s approval was based on results from two Phase 3 clinical trials involving more than 600 patients with relapsing forms of MS.
MSCRG trial
The MSCRG trial enrolled a total of 301 participants with relapsing MS and active disease, as defined by at least two relapses in the prior three years. Patients were randomly assigned to receive either Avonex at a weekly 30 mcg dose, or a placebo, for up to 104 weeks.
The trial’s main goal was to determine the proportion of patients who experienced a sustained increase in disability over the two years of treatment. Worsened disability was defined by increases in the Expanded Disability Status Scale (EDSS) scores, a standard measure used in MS, that lasted at least six months.
The results showed that significantly fewer patients on Avonex than a placebo experienced such a six-month confirmed disability progression (21.9% vs. 34.9%). Treated patients also had significantly fewer disease relapses per year — 0.67 vs. 0.82 with a placebo — and fewer and smaller brain lesions on MRI scans.
CHAMPS trial
The CHAMPS clinical trial involved 383 patients with CIS who were at high risk of transitioning to clinically definite MS. These participants were randomly assigned to receive weekly intramuscular injections of Avonex (30 mcg) or a placebo for three years.
Significantly fewer patients on Avonex than a placebo progressed to clinically definite MS at three years (35% vs. 50%), results from this study showed. These findings represented a 44% reduction in the conversion to clinically definite MS. After 18 months, patients on the active treatment also had significantly fewer new or enlarging brain lesions, as well as lesions with active inflammation.
ASPECT trial
Data from the open-label Phase 3b ASPECT clinical trial (NCT00828204) were used for Biogen’s requests for regulatory approval of the Avonex Pen and the dose titration regimen. The Avonex Pen and the dose titration regimen were approved in Europe and Canada in 2011, and in the U.S. the following year.
In ASPECT, about 74 patients who had been using the prefilled syringe of Avonex for at least 12 weeks were instructed to continue injecting the medication for one additional month using the Avonex Pen.
About 9 in 10 patients were able to successfully use the pen, with most failures taking place during device setup. One error was removing the needle cap manually from the pen rather than extending the injector shield. In one case, a patient also removed the device from the thigh before the medication was administered, which rendered the device unusable. However, 94% of patients preferred the pen over the prefilled syringe.
Ongoing trials
Biogen is assessing the safety and efficacy of Avonex and its other interferon-based therapy, Plegridy, in children and adolescents in an ongoing Phase 3 trial (NCT03958877). A total of 142 patients, ages 10 to 17, with RRMS, are expected to take part. The participants will receive treatment for 96 weeks after which they can continue to receive Plegridy for two more years in a long-term extension phase.
The main goals are to determine the annualized relapse rate and safety. However, investigators also will examine changes in brain lesions, cognition, disability status, and quality of life, as well as time to first relapse. The study is expected to conclude in 2029.
Common side effects of Avonex
The most common side effects of Avonex in clinical trials were flu-like symptoms, such as:
- chills
- fever
- aching muscles
- generalized weakness
Psychological issues
Avonex may cause mental health problems such as depression, psychosis, and suicidal ideation, or thoughts about suicide. These symptoms should immediately be discussed with the care team, and discontinuation may be considered.
Allergic and injection-site reactions
Some people may experience allergic reactions to Avonex or its components. The treatment should not be used in people with known allergies to the medication, and should be discontinued if an allergic reaction occurs.
Injection site reactions also may occur, which in some cases can lead to the death of nearby tissue. Avonex should not be given into an affected area until the skin lesion has resolved.
Liver injury and heart problems
Avonex may cause liver damage. Liver health should be monitored while on Avonex, and the medication stopped if concerning findings are noted.
Heart health also should be tracked in patients with pre-existing heart conditions, as this medicine may worsen some of these diseases.
Low blood cell counts
Post-marketing studies of Avonex have shown that the medication may lower the number of blood cells. Routine assessments of complete blood counts and platelet counts are recommended during treatment with Avonex.
Blood vessel damage
Cases of thrombotic microangiopathy, a condition in which blood clots cause damage to the body’s small blood vessels, have been reported in patients on Avonex. If signs of this disease are noted, the treatment should be discontinued.
Autoimmune diseases
Based on post-marketing reports, patients taking Avonex may develop a number of autoimmune conditions affecting multiple organs. These include idiopathic thrombocytopenia, a condition that results in low platelet levels and easy bruising, thyroid diseases, and autoimmune hepatitis. Discontinuation should be considered if patients develop a new autoimmune disease.
Pregnancy and breastfeeding
Avonex may be used with caution in patients who are pregnant or breastfeeding; patients who are or plan to become pregnant should discuss the benefits and risks of continuing receiving treatment with their healthcare team.
Multiple Sclerosis News Today is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.
FAQs about Avonex
Avonex was approved by the U.S. Food and Drug Administration in May 1996 for the treatment of adults with relapsing-remitting MS and active secondary progressive MS. Its use was expanded in 2003 to include clinically isolated syndrome. The Avonex Pen was approved in the U.S. in 2012.
Yes. While Avonex was previously not recommended for pregnant people, U.S. and European labels were updated in recent years to allow its use in pregnant and breastfeeding patients, where clinically necessary. The decisions were based on data from several European registries showing that exposure to interferon beta-based medications before conception or during the first trimester was not associated with fetal problems. However, people who plan to become pregnant should inform their healthcare provider and discuss the risks and benefits of continuing to receive this treatment during pregnancy.
Avonex may cause liver injury. As such, using this treatment with alcohol or other substances that also can damage the liver may increase the risk of liver problems. Patients who drink alcohol are advised to inform their healthcare providers before starting on this medication.
Some patients may see results as soon as six months after starting treatment. In the CHAMPS trial, which investigated Avonex against a placebo in nearly 400 patients with clinically isolated syndrome, a significant reduction in new brain lesions (both total and with active inflammation) could be observed as early as within six months. However, as each person may respond differently to a given medication, a discussion with a healthcare provider is recommended to better understand when and how Avonex is expected to help a particular patient.
While rare, hair loss and weight changes have been reported in clinical trials as possible side effects of Avonex. Individuals who experience such events should discuss these issues with their healthcare team.
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