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PEGINTERFERON BETA-1A: 12,456 Adverse Event Reports & Safety Profile

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12,456
Total FAERS Reports
312 (2.5%)
Deaths Reported
3,100
Hospitalizations
12,456
As Primary/Secondary Suspect
54
Life-Threatening
44
Disabilities
Biogen Inc.
Manufacturer
Prescription
Status

Drug Class: Interferon beta [EPC] · Route: SUBCUTANEOUS · Manufacturer: Biogen Inc. · FDA Application: 125499 · HUMAN PRESCRIPTION DRUG · FDA Label: Available

First Report: 199201 · Latest Report: 20250830

What Are the Most Common PEGINTERFERON BETA-1A Side Effects?

#1 Most Reported
Influenza like illness
1,431 reports (11.5%)
#2 Most Reported
Injection site erythema
1,041 reports (8.4%)
#3 Most Reported
Multiple sclerosis relapse
945 reports (7.6%)

All PEGINTERFERON BETA-1A Side Effects by Frequency

Side Effect Reports % of Total Deaths Hosp.
Influenza like illness 1,431 11.5% 2 174
Injection site erythema 1,041 8.4% 0 119
Multiple sclerosis relapse 945 7.6% 2 578
Fatigue 673 5.4% 2 142
Headache 587 4.7% 0 105
Pain 580 4.7% 2 111
Injection site reaction 569 4.6% 1 51
Device malfunction 567 4.6% 0 9
Multiple sclerosis 536 4.3% 14 153
Pyrexia 503 4.0% 4 135
Memory impairment 455 3.7% 1 45
Malaise 448 3.6% 3 101
Injection site pain 435 3.5% 0 35
Fall 406 3.3% 5 214
Drug dose omission 389 3.1% 0 12
Drug delivery system malfunction 367 3.0% 0 6
Gait disturbance 360 2.9% 3 103
Drug ineffective 350 2.8% 1 47
Injection site bruising 345 2.8% 0 28
Nausea 322 2.6% 0 73

Who Reports PEGINTERFERON BETA-1A Side Effects? Age & Gender Data

Gender: 82.0% female, 18.0% male. Average age: 49.2 years. Most reports from: US. View detailed demographics →

Is PEGINTERFERON BETA-1A Getting Safer? Reports by Year

YearReportsDeathsHosp.
2001 1 0 1
2003 1 0 0
2005 5 1 2
2006 1 0 0
2007 2 0 0
2008 2 0 0
2010 4 0 1
2011 7 0 2
2012 1 0 0
2013 12 0 6
2014 146 3 69
2015 1,216 22 498
2016 1,184 22 392
2017 729 24 265
2018 774 17 276
2019 663 16 246
2020 455 18 179
2021 454 22 170
2022 375 21 117
2023 201 12 60
2024 177 12 35
2025 74 8 11

View full timeline →

What Is PEGINTERFERON BETA-1A Used For?

IndicationReports
Multiple sclerosis 11,105
Product used for unknown indication 817
Relapsing-remitting multiple sclerosis 390
Maternal exposure timing unspecified 82
Secondary progressive multiple sclerosis 11
Demyelination 7
Relapsing multiple sclerosis 6

PEGINTERFERON BETA-1A vs Alternatives: Which Is Safer?

PEGINTERFERON BETA-1A vs PEGINTRON PEGINTERFERON BETA-1A vs PEGLOTICASE PEGINTERFERON BETA-1A vs PEGUNIGALSIDASE ALFA-IWXJ PEGINTERFERON BETA-1A vs PEGVALIASE-PQPZ PEGINTERFERON BETA-1A vs PEGVISOMANT PEGINTERFERON BETA-1A vs PEGZEREPOETIN ALFA PEGINTERFERON BETA-1A vs PEMBROLIZUMAB PEGINTERFERON BETA-1A vs PEMETREXED PEGINTERFERON BETA-1A vs PEMIGATINIB PEGINTERFERON BETA-1A vs PENICILLAMINE

Other Drugs in Same Class: Interferon beta [EPC]

Official FDA Label for PEGINTERFERON BETA-1A

Official prescribing information from the FDA-approved drug label.

Drug Description

Peginterferon beta-1a is a covalent conjugate of recombinant interferon beta-1a (approximate molecular weight [MW] 20,000 daltons) with a single, linear methoxy poly(ethyleneglycol)-O-2-methylpropionaldehyde molecule (approximate MW 20,000 daltons). Interferon beta-1a is produced as a glycosylated protein using genetically-engineered Chinese hamster ovary cells into which the human interferon beta gene has been introduced. The amino acid sequence of recombinant interferon beta-1a is identical to that of the human interferon beta counterpart. The molecular weight of peginterferon beta-1a is approximately 44,000 daltons, consistent with the mass of the protein, the carbohydrate moieties (approximately 2,500 daltons), and the attached poly(ethylene glycol). Peginterferon beta-1a 125 mcg contains 125 mcg of interferon beta-1a plus 125 mcg of poly(ethylene glycol). Using the World Health Organization International Standard for interferon beta, peginterferon beta-1a has a specific antiviral activity of approximately 100 million International Units (MIU) per mg of protein as determined using an in vitro cytopathic effect assay. Peginterferon beta-1a 125 mcg contains approximately 12 MIU of antiviral activity.

Subcutaneous

Administration PLEGRIDY (peginterferon beta-1a) injection is a sterile, preservative-free solution in a single-dose prefilled pen or single-dose prefilled syringe with a 29-gauge, 0.5-inch needle for subcutaneous use. Each prefilled pen or prefilled syringe delivers 0.5 mL.

Each

0.5 mL contains 63 mcg, 94 mcg, or 125 mcg of peginterferon beta-1a, and L-arginine HCl (15.8 mg), glacial acetic acid (0.25 mg), polysorbate 20 (0.025 mg), and sodium acetate trihydrate (0.79 mg) in Water for Injection, USP. The pH is approximately 4.8.

Intramuscular

Administration PLEGRIDY (peginterferon beta-1a) injection is a sterile, preservative-free solution in a single-dose prefilled syringe with a 23-gauge, 1.25-inch needle for intramuscular use. Each prefilled syringe delivers 0.5 mL.

Each

0.5 mL contains 125 mcg of peginterferon beta-1a, and L-arginine HCl (15.8 mg), glacial acetic acid (0.25 mg), polysorbate 20 (0.025 mg), and sodium acetate trihydrate (0.79 mg) in Water for Injection, USP. The pH is approximately 4.8.

FDA Approved Uses (Indications)

AND USAGE PLEGRIDY is indicated for the treatment of relapsing forms of multiple sclerosis (MS), to include clinically isolated syndrome, relapsing-remitting disease, and active secondary progressive disease, in adults. PLEGRIDY is an interferon beta indicated for the treatment of relapsing forms of multiple sclerosis (MS), to include clinically isolated syndrome, relapsing-remitting disease, and active secondary progressive disease, in adults ( 1 )

Dosage & Administration

AND ADMINISTRATION For subcutaneous or intramuscular use only ( 2.1 ) Recommended dose: 125 micrograms every 14 days ( 2.1 ) PLEGRIDY dose should be titrated, starting with 63 micrograms on day 1, 94 micrograms on day 15, and 125 micrograms (full dose) on day 29 ( 2.1 ) A healthcare professional should train patients in the proper technique for self-administering subcutaneous injections using the prefilled pen or syringe or intramuscular injections using the prefilled syringe ( 2.2 ) Analgesics and/or antipyretics on treatment days may help ameliorate flu-like symptoms ( 2.3 )

2.1 Dosing Information PLEGRIDY may only be administered subcutaneously (SC) or intramuscularly (IM).

Recommended Maintenance Dosage

After initial titration (see Table 1 and Table 2 ), the recommended dosage of PLEGRIDY is 125 micrograms injected every 14 days. For subcutaneous injection: Patients may rotate injection sites between the abdomen, back of the upper arm, or thigh. For intramuscular injection: Patients may rotate injection sites between the left and right thighs.

Treatment Initiation

Dose titration at the initiation of treatment may help to ameliorate flu-like symptoms that can occur at treatment initiation with interferons. Prophylactic and concurrent use of analgesics and/or antipyretics may prevent or ameliorate flu-like symptoms sometimes experienced during treatment with PLEGRIDY. Switching between the subcutaneous and intramuscular routes of administration and vice versa has not been studied. It is not expected that dose titration should be repeated to ameliorate flu-like symptoms if switching between subcutaneous and intramuscular routes of administration, or vice versa based upon bioequivalence demonstrated between the two routes of administration.

Subcutaneous

Administration of PLEGRIDY Patients using PLEGRIDY for the first time should start treatment with 63 micrograms on day 1. On day 15 (14 days later), the dose is increased to 94 micrograms, reaching the full dose of 125 micrograms on day 29 (after another 14 days). Patients continue with the full dose (125 micrograms) every 14 days thereafter (see Table 1 ). A PLEGRIDY Starter Pack is available containing two prefilled pens or syringes: 63 micrograms (dose 1) and 94 micrograms (dose 2).

Table

1: Schedule for Subcutaneous Dose Titration Dose Time a Amount (micrograms) Color of Pen or Syringe Label a Dosed every 14 days Dose 1 On day 1 63 Orange Dose 2 On day 15 94 Blue Dose 3 On day 29 and every 14 days thereafter 125 (full dose)

Grey Intramuscular

Administration of PLEGRIDY For patients using PLEGRIDY injected intramuscularly for the first time, PLEGRIDY should be titrated using the PLEGRIDY Titration Kit designed for use with the prefilled syringe. The PLEGRIDY Titration Kit is supplied separately and contains two titration devices to be used only with PLEGRIDY prefilled syringes for intramuscular use. Patients should start treatment with 63 micrograms (yellow clip) on day 1. On day 15 (14 days later), the dose is increased to 94 micrograms (purple clip), reaching the full dose of 125 micrograms on day 29 (after another 14 days). Patients continue with the full dose (125 micrograms) every 14 days thereafter (see Table 2 ).

Table

2: Schedule for Intramuscular Dose Titration Dose Time a Amount (micrograms)

Titration

Clip a Dosed every 14 days Dose 1 On day 1 63 Yellow Dose 2 On day 15 94 Purple Dose 3 On day 29 and every 14 days thereafter 125 (full dose)

No Clips

Needed

2.2 Important Administration Instructions (All Dosage Forms) Healthcare professionals should train patients in the proper technique for self-administering subcutaneous injections using the prefilled pen or syringe or intramuscular injections using the prefilled syringe. Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration. Advise patients and caregivers to rotate injection sites with each administration to minimize the likelihood of severe injection site reactions, including necrosis or localized infection <span class="opacity-50 text-xs">[see Warnings and Precautions ( 5.4 ) ]</span>. Once removed from the refrigerator, PLEGRIDY should be allowed to warm to room temperature (about 30 minutes) prior to injection. Do not use external heat sources such as hot water to warm PLEGRIDY. Each PLEGRIDY pen and syringe for subcutaneous injection is provided with the needle pre-attached. PLEGRIDY prefilled syringe for intramuscular injection is supplied as a prefilled syringe with a separate needle. Both intramuscular and subcutaneous prefilled syringes and subcutaneously administered prefilled pens are for one-time use in one patient only and should be discarded after use.

2.3 Premedication for Flu-like Symptoms Prophylactic and concurrent use of analgesics and/or antipyretics may prevent or ameliorate flu-like symptoms sometimes experienced during treatment with PLEGRIDY.

Contraindications

PLEGRIDY is contraindicated in patients with a history of hypersensitivity to natural or recombinant interferon beta or peginterferon, or any other component of PLEGRIDY [see Warnings and Precautions ( 5.3 )] . History of hypersensitivity to natural or recombinant interferon beta or peginterferon, or any other component of PLEGRIDY ( 4 )

Known Adverse Reactions

REACTIONS The following serious adverse reactions are discussed in more detail in other sections of labeling: Hepatic Injury [see Warnings and Precautions ( 5.1 )] Depression and Suicide [see Warnings and Precautions ( 5.2 )] Anaphylaxis and Other Allergic Reactions [see Warnings and Precautions ( 5.3 )]

Injection Site Reactions Including

Necrosis [see Warnings and Precautions ( 5.4 )]

Congestive Heart

Failure [see Warnings and Precautions (Section 5.5 )]

Decreased Peripheral Blood

Counts [see Warnings and Precautions ( 5.6 )]

Thrombotic

Microangiopathy [see Warnings and Precautions ( 5.7 )]

Pulmonary Arterial

Hypertension [see Warnings and Precautions ( 5.8 )]

Autoimmune

Disorders [see Warnings and Precautions ( 5.9 )] Seizures [see Warnings and Precautions ( 5.10 )] The most common adverse reactions in clinical trials of subcutaneous PLEGRIDY (incidence ≥10% and at least 2% more frequent on PLEGRIDY than on placebo) were injection site erythema, influenza-like illness, pyrexia, headache, myalgia, chills, injection site pain, asthenia, injection site pruritus, and arthralgia ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Biogen at 1-800-456-2255 or FDA at 1-800-FDA-1088 or http://www.fda.gov/medwatch.

6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of PLEGRIDY cannot be directly compared to rates in clinical trials of other drugs and may not reflect the rates observed in practice.

Plegridy

Via Subcutaneous Administration In clinical studies (Study 1 and Study 2), a total of 1468 patients with relapsing multiple sclerosis received PLEGRIDY by subcutaneous injection for up to 177 weeks (41 months), with an overall exposure equivalent to 1932 person-years. A total of 1093 patients received at least 1 year, and 415 patients at least 2 years of treatment with PLEGRIDY. A total of 512 and 500 patients, respectively, received PLEGRIDY 125 micrograms every 14 days or every 28 days during the placebo-controlled phase of Study 1 (year 1). The experience in year 2 of Study 1 and in the 2-year safety extension study (Study 2) was consistent with the experience in the 1-year placebo-controlled phase of Study 1. In the placebo-controlled phase of Study 1, the most common adverse drug reactions for PLEGRIDY 125 micrograms subcutaneously every 14 days were injection site erythema, influenza-like illness, pyrexia, headache, myalgia, chills, injection site pain, asthenia, injection site pruritus, and arthralgia (all had incidence more than 10% and at least 2% more than placebo). The most commonly reported adverse event leading to discontinuation in patients treated with PLEGRIDY 125 micrograms subcutaneously every 14 days was influenza-like illness (in less than 1% of patients).

Table

3 summarizes adverse reactions reported over 48 weeks from patients treated in the placebo-controlled phase of Study 1 who received subcutaneous PLEGRIDY 125 micrograms (n=512), or placebo (n=500), every 14 days.

Table

3: Adverse Reactions in the 48-Week Placebo-Controlled Phase of Study 1 with an Incidence 2% Higher for PLEGRIDY Than for Placebo PLEGRIDY (N=512) % Placebo (N=500) % Nervous System Disorders Headache 44 33 Gastrointestinal Disorders Nausea 9 6 Vomiting 5 2 Musculoskeletal and Connective Tissue Disorders Myalgia 19 6 Arthralgia 11 7 General Disorders and Administration Site Conditions Injection site erythema 62 7 Influenza like illness 47 13 Pyrexia 45 15 Chills 17 5 Injection site pain 15 3 Asthenia 13 8 Injection site pruritus 13 1 Hyperthermia 4 1 Pain 5 3 Injection site edema 3 0 Injection site warmth 3 0 Injection site hematoma 3 1 Injection site rash 2 0 Investigations Body temperature increased 6 3 Alanine aminotransferase increased 6 3 Aspartate aminotransferase increased 4 2 Gamma-glutamyl-transferase increased 3 1 Skin and Subcutaneous Tissue Disorder Pruritus 4 1 Flu-Like Symptoms Influenza-like illness was experienced by 47% of patients receiving PLEGRIDY 125 micrograms every 14 days and 13% of patients receiving placebo. Fewer than 1% of PLEGRIDY-treated patients in Study 1 discontinued treatment due to flu-like symptoms.

Comparison Between

Subcutaneous and Intramuscular Administration An open-label, crossover study analyzed findings from 130 healthy volunteers to assess the bioequivalence of single doses of 125 micrograms of PLEGRIDY administered as a subcutaneous and intramuscular injection (Study 3). The most commonly reported adverse reactions (with >10% incidence in either arm) across both treatment periods were chills (36% in IM vs 27% in SC), pain (22% in IM vs 14% in SC), headache (36% in IM vs 41% in SC), injection site pain (11% in IM vs 15% in SC), and injection site erythema (2% in IM vs 25% in SC). Overall, injection site reactions were reported in 14% via IM route as compared to 32% via SC route.

6.2 Immunogenicity As with all therapeutic proteins, there is a potential for immunogenicity. The detection of antibody formation is highly dependent on the sensitivity and specificity of the assay. Additionally, the observed incidence of antibody (including neutralizing antibody) positivity in an assay may be influenced by several factors including assay methodology, sample handling, timing of sample collection, concomitant medications, and underlying disease. For these reasons, comparison of the incidence of antibodies in the studies described below with the incidence of antibodies in other studies or to other interferon beta-1a products may be misleading.

In Study

1, fewer than 1% of patients treated with PLEGRIDY SC every 14 days for 1 year developed neutralizing antibodies.

Approximately

7% of PLEGRIDY SC-treated patients developed antibodies to the polyethylene glycol moiety. No formal studies have been conducted with regards to immunogenicity of the intramuscular route of administration of PLEGRIDY.

6.3 Postmarketing Experience The following adverse reactions have been identified during post-approval use of PLEGRIDY. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. Anaphylactic reactions In post marketing experience, serious hypersensitivity reactions, including cases of anaphylaxis, have been reported following PLEGRIDY administration <span class="opacity-50 text-xs">[see Warnings and Precautions ( 5.3 )]</span>. Hepatic injury In post marketing experience, noninfectious hepatitis (including serious hepatitis) cases have been reported following PLEGRIDY administration <span class="opacity-50 text-xs">[see Warnings and Precautions ( 5.1 )]</span> .

Pulmonary Arterial

Hypertension In postmarketing experience, pulmonary arterial hypertension has been reported following PLEGRIDY administration [see Warnings and Precautions ( 5.8 )] .

Warnings

AND PRECAUTIONS Hepatic injury: monitor liver function tests; monitor patients for signs and symptoms of hepatic injury; consider discontinuation of PLEGRIDY if hepatic injury occurs ( 5.1 ) Depression and suicide: advise patients to report immediately any symptom of depression or suicidal ideation to their healthcare provider; consider discontinuation of PLEGRIDY if depression occurs ( 5.2 ) Anaphylaxis and other allergic reactions: Discontinue PLEGRIDY if a serious allergic reaction occurs ( 5.3 ) Injection site reactions: Do not administer PLEGRIDY into affected area until fully healed; if multiple lesions occur, change injection site or discontinue PLEGRIDY until healing of skin lesions ( 5.4 ) Congestive heart failure: monitor patients with pre-existing significant cardiac disease for worsening of cardiac symptoms ( 5.5 ) Decreased peripheral blood counts: monitor complete blood counts ( 5.6 )

Thrombotic

Microangiopathy: Cases of thrombotic microangiopathy have been reported with interferon beta products. Discontinue PLEGRIDY if clinical symptoms and laboratory findings consistent with TMA occur ( 5.7 )

Pulmonary Arterial

Hypertension: Cases of pulmonary arterial hypertension (PAH) have been reported in patients treated with interferon beta products, including PLEGRIDY. Discontinue PLEGRIDY if PAH is diagnosed ( 5.8 ) Autoimmune disorders: consider discontinuation of PLEGRIDY if a new autoimmune disorder occurs ( 5.9 )

5.1 Hepatic Injury Severe hepatic injury, including hepatitis, autoimmune hepatitis, and rare cases of severe hepatic failure, have been reported with interferon beta. Asymptomatic elevation of hepatic transaminases has also been reported, and in some patients has recurred upon rechallenge with interferon beta. Elevations in hepatic enzymes and hepatic injury have been observed with the use of PLEGRIDY in clinical studies. The incidence of increases in hepatic transaminases was greater in patients taking PLEGRIDY than in those taking placebo. The incidence of elevations of alanine aminotransferase above 5 times the upper limit of normal was 1% in placebo-treated patients and 2% in PLEGRIDY-treated patients. The incidence of elevations of aspartate aminotransferase above 5 times the upper limit of normal was less than 1% in placebo-treated patients and less than 1% in PLEGRIDY-treated patients. Elevations of serum hepatic transaminases combined with elevated bilirubin occurred in 2 patients. Both cases resolved following discontinuation of PLEGRIDY. Cases of noninfectious hepatitis have been reported in the postmarketing setting with use of PLEGRIDY. Monitor patients for signs and symptoms of hepatic injury.

5.2 Depression and Suicide Depression, suicidal ideation, and suicide occur more frequently in patients receiving interferon beta than in patients receiving placebo. In clinical studies, the overall incidence of adverse events related to depression and suicidal ideation in multiple sclerosis patients was 8% in both the PLEGRIDY and placebo groups. The incidence of serious events related to depression and suicidal ideation was similar and less than 1% in both groups. Advise patients to report immediately any symptom of depression or suicidal ideation to their healthcare provider. If a patient develops depression or other severe psychiatric symptoms, consider stopping treatment with PLEGRIDY.

5.3 Anaphylaxis and Other Allergic Reactions Serious allergic reactions are rare complications of treatment with interferon beta; anaphylaxis has been reported with use of PLEGRIDY in the postmarketing setting. Less than 1% of PLEGRIDY-treated patients experienced a serious allergic reaction such as angioedema or urticaria. Those who did have serious allergic reactions recovered promptly after treatment with antihistamines or corticosteroids. Discontinue PLEGRIDY if a serious allergic reaction occurs. The protective rubber cover of the PLEGRIDY prefilled syringe for intramuscular administration contains natural rubber latex which may cause allergic reactions and should not be handled by latex-sensitive individuals. The safe use of PLEGRIDY prefilled syringe in latex-sensitive individuals has not been studied.

5.4 Injection Site Reactions Including Necrosis Injection site reactions, including injection site necrosis, can occur with the use of interferon beta, including PLEGRIDY. In clinical studies of subcutaneous PLEGRIDY, the incidence of injection site reactions (e.g., injection site erythema, pain, pruritus, or edema) was 66% in the PLEGRIDY group and 11% in the placebo group; the incidence of severe injection site reactions was 3% in the PLEGRIDY group and 0% in the placebo group. One patient out of 1468 patients who received PLEGRIDY in clinical studies experienced injection site necrosis. The injury resolved with standard medical treatment.

In Study

3, which compared single doses of intramuscular and subcutaneous PLEGRIDY [see Adverse Reactions ( 6.1 )] , the incidence of injection site reactions (e.g., injection site erythema, pain, pruritus, or edema) was 14% in the intramuscular PLEGRIDY group and 32% in the subcutaneous PLEGRIDY group. Injection site abscesses and cellulitis have been reported in the postmarketing setting with use of interferon beta. Some cases required treatment with hospitalization for surgical drainage and intravenous antibiotics. Periodically evaluate patient understanding and use of aseptic self-injection techniques and procedures, particularly if injection site necrosis has occurred. Decisions to discontinue therapy following necrosis at a single injection site should be based on the extent of the necrosis. For patients who continue therapy with PLEGRIDY after injection site necrosis has occurred, avoid administration of PLEGRIDY near the affected area until it is fully healed. If multiple lesions occur, change injection site or discontinue PLEGRIDY until healing occurs.

5.5 Congestive Heart Failure Congestive heart failure, cardiomyopathy, and cardiomyopathy with congestive heart failure occur in patients receiving interferon beta. In clinical studies, the incidence of cardiovascular events was 7% in both PLEGRIDY and placebo treatment groups. No serious cardiovascular events were reported in the PLEGRIDY group. Monitor patients with significant cardiac disease for worsening of their cardiac condition during initiation and continuation of treatment with PLEGRIDY.

5.6 Decreased Peripheral Blood Counts Interferon beta can cause decreased peripheral blood counts in all cell lines, including rare instances of pancytopenia and severe thrombocytopenia. In clinical studies, decreases in white blood cell counts below 3.0 x 10 9 /L occurred in 7% of patients receiving PLEGRIDY and in 1% receiving placebo. There is no apparent association between decreases in white blood cell counts and an increased risk of infections or serious infections. The incidence of clinically significant decreases in lymphocyte counts (below 0.5 x 10 9 /L), neutrophil counts (below 1.0 x 10 9 /L), and platelet counts (below 100 x 10 9 /L) were all less than 1% and similar in both placebo and PLEGRIDY groups. Two serious cases were reported in patients treated with PLEGRIDY: one patient (less than 1%) experienced severe thrombocytopenia (defined as a platelet count less than or equal to 10 x 10 9 /L), and another patient (less than 1%) experienced severe neutropenia (defined as a neutrophil count less than or equal to 0.5 x 10 9 /L). In both patients, cell counts recovered after discontinuation of PLEGRIDY. Compared to placebo, there were no significant differences in red blood cell counts in patients treated with PLEGRIDY. Monitor patients for infections, bleeding, and symptoms of anemia. Monitor complete blood cell counts, differential white blood cell counts, and platelet counts during treatment with PLEGRIDY. Patients with myelosuppression may require more intensive monitoring of blood cell counts.

5.7 Thrombotic Microangiopathy Cases of thrombotic microangiopathy (TMA), including thrombotic thrombocytopenic purpura and hemolytic uremic syndrome, some fatal, have been reported with interferon beta products. Cases have been reported several weeks to years after starting interferon beta products. Discontinue PLEGRIDY if clinical symptoms and laboratory findings consistent with TMA occur, and manage as clinically indicated.

5.8 Pulmonary Arterial Hypertension Cases of pulmonary arterial hypertension (PAH) have been reported in patients treated with interferon beta products, including PLEGRIDY. PAH has occurred in patients treated with interferon beta products in the absence of other contributory factors. Many of the reported cases required hospitalization, including one case with interferon beta in which the patient underwent a lung transplant. PAH has developed at various time points after initiating therapy with interferon beta products and may occur several years after starting treatment. Patients who develop unexplained symptoms (e.g., dyspnea, new or increasing fatigue) should be assessed for PAH. If alternative etiologies have been ruled out and a diagnosis of PAH is confirmed, discontinue treatment and manage as clinically indicated.

5.9 Autoimmune Disorders Autoimmune disorders of multiple target organs including idiopathic thrombocytopenia, hyper- and hypothyroidism, and autoimmune hepatitis have been reported with interferon beta. In clinical studies, the incidence of autoimmune disorders was less than 1% in both PLEGRIDY and placebo treatment groups. If patients develop a new autoimmune disorder, consider stopping PLEGRIDY.

5.10 Seizures Seizures are associated with the use of interferon beta. The incidence of seizures in multiple sclerosis clinical studies was less than 1% in patients receiving PLEGRIDY and placebo. Exercise caution when administering PLEGRIDY to patients with a seizure disorder.