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Development of ENBREL

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ENBREL clinical experience

In 1989, scientists at Immunex began an effort to isolate the gene for the receptor for tumor necrosis factor (TNF). Within 3 months, they were successful in isolating and cloning it. However, this initial triumph was only the beginning of a 9 year process to develop the therapy called ENBREL, one of the first in a class of drugs known as biologic response modifiers.

Designing a protein

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Having isolated the gene, scientists at Immunex set out to create a protein from it. They used recombinant DNA technology to produce an early version of ENBREL that was a monomeric molecule (ie, a single-strand protein). This monomeric protein did not function as anticipated, making it only partially active against TNF.

Having found the right structure for the molecule, named etanercept, scientists began to test it in the laboratory on animals. These tests showed dramatic effects on the course of arthritis and other inflammatory diseases in mice. As a result, etanercept was deemed to be promising enough to warrant testing in human subjects.

Manufacturing ENBREL: precision at every step

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How ENBREL is made

Biotech drugs such as ENBREL are much more difficult, time-consuming, and expensive to make than a typical medication. ENBREL is a large protein molecule, which means it has many components and is especially difficult to make. The average weight of a small pharmaceutical drug is around 500 daltons. A protein such as insulin weighs around 5,000 daltons. ENBREL, by contrast, weighs about 150,000 daltons. If even one aspect or part of the molecule is altered during manufacturing, the protein could be ineffective. When this happens, the lot must be discarded and the whole process must start over again.

The manufacturing process for ENBREL includes the following seven steps:

Step 1: Reproducing the gene
The first step is to synthesize the gene encoding for ENBREL. Before it can produce a medicine such as ENBREL, the gene has to be inserted into a living cell called a host cell.

Step 2: Enabling the host cells to thrive
The host cells must be treated with great care. They are kept in bioreactors; two-story vats filled with a life-sustaining bath of nutrients. By carefully monitoring and controlling the temperature, acidity, and oxygen level in the bioreactors, scientists enable the host cells to produce the desired protein, ENBREL. This is an extremely delicate process.

Step 3: Harvesting
When the batch is ready, the host cells are removed and the broth containing ENBREL is harvested from the bioreactor for purification.

Step 4: Purifying
After harvesting, the broth containing ENBREL passes through various purification steps to ensure that the ENBREL protein molecules are separated from other materials.

Step 5: Testing and quality control
ENBREL moves through a complex cycle of tests. This extensive quality control ensures that anything that is not the pure ENBREL protein is removed.

Step 6: Placing into vials and lyophilization
After rigorous testing, ENBREL is put into sterile vials while still in liquid form. Through a process called lyophilization (freeze drying), all the moisture is removed. The dry powder that remains is the final product.

Step 7: Ready for distribution
The dried product is tested again for purity, and is then labeled and refrigerated. The ENBREL is now ready to be packaged and shipped.

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Important Safety Information

Risk of Serious Infections
Infections, including serious infections leading to hospitalization or death, have been observed in patients treated with ENBREL. Infections have included bacterial sepsis and tuberculosis. Patients should be educated about the symptoms of infection and closely monitored for signs and symptoms of infection during and after treatment with ENBREL. Patients who develop an infection should be evaluated for appropriate antimicrobial treatment and, in patients who develop a serious infection, ENBREL should be discontinued.

Tuberculosis (frequently disseminated or extrapulmonary at clinical presentation) has been observed in patients receiving TNF-blocking agents, including ENBREL. Tuberculosis may be due to reactivation of latent tuberculosis infection or to new infection. Data from clinical trials and preclinical studies suggest that the risk of reactivation of latent tuberculosis infection is lower with ENBREL than with TNF-blocking monoclonal antibodies. Nonetheless, postmarketing cases of tuberculosis reactivation have been reported for TNF blockers, including ENBREL. Patients should be evaluated for tuberculosis risk factors and be tested for latent tuberculosis infection prior to initiating ENBREL and during treatment. Treatment of latent tuberculosis infection should be initiated prior to therapy with ENBREL. Treatment of latent tuberculosis in patients with a reactive tuberculin test reduces the risk of tuberculosis reactivation in patients receiving TNF blockers. Some patients who tested negative for latent tuberculosis prior to receiving ENBREL have developed active tuberculosis. Physicians should monitor patients receiving ENBREL for signs and symptoms of active tuberculosis, including patients who tested negative for latent tuberculosis infection.

Many of these serious infections occurred in patients predisposed to infection because of concomitant immunosuppressive therapy and/or their underlying disease. Do not start ENBREL in the presence of sepsis, active infections (including chronic or localized), or allergy to ENBREL or its components. Use caution in patients predisposed to infection, such as those with advanced or poorly controlled diabetes.

Neurologic Events
TNF inhibitors, including ENBREL, have been associated with rare cases of new onset or exacerbation of CNS demyelinating disorders (some presenting with mental status changes and some associated with permanent disability). Transverse myelitis, optic neuritis, multiple sclerosis, and cases of new onset or exacerbation of seizure disorders have been observed in association with ENBREL therapy. The causal relationship to ENBREL therapy remains unclear. Exercise caution when considering ENBREL for patients with these disorders.

Hematologic Events
Rare cases of pancytopenia, including aplastic anemia, some fatal, have been reported. The causal relationship to ENBREL therapy is unclear. Exercise caution in patients who have a previous history of significant hematologic abnormalities. Advise patients to seek immediate medical attention if they develop signs or symptoms of blood dyscrasias or infection. Consider discontinuing ENBREL if significant hematologic abnormalities are confirmed.

Malignancies
In clinical trials of all TNF inhibitors, more cases of lymphoma were seen compared to control patients. The risk of lymphoma may be up to several-fold higher in RA and psoriasis patients; the role of TNF inhibitors in the development of malignancies is unknown. In clinical trials, the incidence of malignancies other than lymphoma has not increased with exposure to ENBREL and is similar to what would be expected in the general population.

Hepatitis B Reactivation
TNF inhibitors, including ENBREL, have been associated reactivation of hepatitis B virus (HBV) in chronic carriers of this virus. The majority of these reports occurred in patients on concomitant immunosuppressive agents, which may also contribute to HBV reactivation. Prescribers should exercise caution in prescribing TNF blockers for patients identified as carriers of HBV.

Adverse Events
The most commonly reported adverse events in RA clinical trials were injection site reaction, infection, and headache. In clinical trials of all other adult indications, adverse events were similar to those reported in RA clinical trials. In a JIA study, infection, headache, abdominal pain, vomiting, and nausea occurred more frequently than in adult RA patients in placebo controlled trials. The types of infections reported in JIA patients were generally mild and consistent with those commonly seen in outpatient pediatric populations.

Please see Prescribing Information and Medication Guide.

INDICATIONS
Moderate to Severe Rheumatoid Arthritis (RA)
ENBREL is indicated for reducing signs and symptoms, inducing major clinical response, inhibiting the progression of structural damage, and improving physical function in patients with moderately to severely active rheumatoid arthritis. ENBREL can be initiated in combination with methotrexate (MTX) or used alone.

  • In medical studies, ENBREL was shown to be effective in about 2 out of 3 adults with RA who used it, and has been shown to begin working in as few as 2 weeks, with most patients receiving benefit within 3 months. In an RA medical study, 55% of patients had no progression of joint damage.

Moderate to Severe Polyarticular Juvenile Idiopathic Arthritis (JIA)
ENBREL is indicated for reducing signs and symptoms of moderately to severely active polyarticular juvenile idiopathic arthritis in patients ages 2 and older.

  • In a medical study, ENBREL was shown to be effective in about 3 out of 4 children with JIA who used it. For these JIA patients, ENBREL has been shown to begin working in approximately 2 to 4 weeks.

Psoriatic Arthritis
ENBREL is indicated for reducing signs and symptoms, inhibiting the progression of structural damage of active arthritis, and improving physical function in patients with psoriatic arthritis. ENBREL can be used in combination with methotrexate in patients who do not respond adequately to methotrexate alone.

  • In a medical study, ENBREL was shown to be effective in about 50% of psoriatic arthritis patients who used it. Clinical responses were apparent at the time of the first visit (4 weeks) and were maintained through 6 months of therapy.

Ankylosing Spondylitis (AS)
ENBREL is indicated for reducing signs and symptoms in patients with active ankylosing spondylitis.

  • In a medical study, ENBREL was shown to be effective in about 3 out of 5 adults with AS who used it. Clinical responses were seen at 2 weeks in 46% of patients, with 59% of patients receiving benefit within 8 weeks.

Moderate to Severe Plaque Psoriasis
ENBREL is indicated for the treatment of adult patients (18 years or older) with chronic moderate to severe plaque psoriasis who are candidates for systemic therapy or phototherapy.

  • In medical studies, nearly half of patients saw a significant improvement in their plaque psoriasis within 3 months of using ENBREL. Overall, 3 out of 4 patients saw improvement. ENBREL can work fast; many patients saw improvement within 2 months. ENBREL has been shown to be effective through 12 months of therapy.
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