Eculizumab

The dosage of Eculizumab varies significantly depending on the specific condition being treated. Healthcare providers follow a structured induction and maintenance schedule.

• Paroxysmal Nocturnal Hemoglobinuria (PNH):
• Induction Phase: 600 mg via IV infusion once every 7 days for the first 4 weeks.
• Maintenance Phase: 900 mg for the fifth dose (1 week after the 4th dose), followed by 900 mg every 14 days thereafter.
• Atypical Hemolytic Uremic Syndrome (aHUS):
• Induction Phase: 900 mg via IV infusion once every 7 days for the first 4 weeks.
• Maintenance Phase: 1200 mg for the fifth dose (1 week after the 4th dose), followed by 1200 mg every 14 days thereafter.
• Generalized Myasthenia Gravis (gMG) and NMOSD:
• Induction Phase: 900 mg via IV infusion once every 7 days for the first 4 weeks.
• Maintenance Phase: 1200 mg for the fifth dose (1 week after the 4th dose), followed by 1200 mg every 14 days thereafter.

Eculizumab is approved for use in pediatric patients for the treatment of PNH and aHUS. The dosage is strictly based on body weight. For example:

• Patients 40 kg or greater: Follow the adult dosing schedule.
• Patients 30 kg to <40 kg: 600 mg weekly for 2 weeks (induction), followed by 900 mg every 2 weeks (maintenance).
• Patients 20 kg to <30 kg: 600 mg weekly for 2 weeks (induction), followed by 600 mg every 2 weeks (maintenance).
• Patients 10 kg to <20 kg: 600 mg once (induction), followed by 300 mg every 2 weeks (maintenance).
• Patients 5 kg to <10 kg: 300 mg once (induction), followed by 300 mg every 3 weeks (maintenance).

Renal Impairment

No dosage adjustments are typically required for patients with renal (kidney) impairment. Eculizumab is not cleared by the kidneys, and clinical studies have shown that its pharmacokinetics are not significantly altered in patients with various degrees of renal dysfunction.

Hepatic Impairment

No specific dosage adjustments are recommended for patients with hepatic (liver) impairment. As a monoclonal antibody, it is not metabolized by the liver's enzymatic pathways.

Elderly Patients

Clinical studies have not identified significant differences in safety or efficacy between patients over 65 and younger patients. However, healthcare providers usually exercise caution when dosing elderly patients due to the higher frequency of co-existing medical conditions.

Eculizumab is administered exclusively as an intravenous infusion by a trained healthcare professional. It is not for self-administration.

• Preparation: The vial must be inspected for particulate matter and discoloration. It is then diluted to a final concentration of 5 mg/mL.
• Infusion Time: The infusion typically takes 35 minutes for adults and may take up to 4 hours for pediatric patients.
• Monitoring: Patients are usually monitored for at least one hour following the infusion for signs of infusion-related reactions, such as fever, chills, or difficulty breathing.
• Storage: Unopened vials must be stored in a refrigerator at 2°C to 8°C (36°F to 46°F) and protected from light. Do not freeze or shake the vials.

Consistency is critical for Eculizumab therapy. If a dose is missed, it should be administered as soon as possible. If the dose is more than 2 or 3 days late, your healthcare provider may need to adjust the subsequent schedule to ensure complement inhibition remains continuous. For patients with PNH or aHUS, missing a dose can lead to a rapid return of hemolysis or blood vessel damage.

There is limited information regarding Eculizumab overdose. Because it is administered by healthcare professionals, the risk of accidental overdose is low. In the event of a suspected overdose, the patient should be monitored for signs of adverse reactions, and supportive care should be provided as needed.

> Important: Follow your healthcare provider's dosing instructions exactly. Do not adjust your dose or skip infusions without medical guidance, as this can lead to severe complications.

Most patients receiving Eculizumab will experience some side effects, particularly during the first few months of treatment. These are generally manageable but should be reported to a doctor.

• Headache: This is the most frequently reported side effect. It often occurs shortly after the infusion and may range from mild to severe. It typically resolves within 24–48 hours.
• Nasopharyngitis: Symptoms similar to the common cold, including a sore throat, runny nose, or nasal congestion.
• Nausea and Vomiting: Some patients experience digestive upset during or after the infusion.
• Back Pain and Arthralgia (Joint Pain): Generalized body aches or localized pain in the back or joints are common.
• Fatigue: A persistent feeling of tiredness or lack of energy.

• Dizziness: A feeling of lightheadedness or vertigo.
• Hypertension (High Blood Pressure): Some patients may see a temporary or sustained increase in blood pressure.
• Upper Respiratory Tract Infections: Increased susceptibility to bronchitis or sinus infections.
• Edema (Swelling): Swelling in the legs, ankles, or feet due to fluid retention.
• Herpes Simplex Infections: Reactivation of cold sores or other herpes-related symptoms.

• Infusion-Related Reactions: Rare but serious reactions during the infusion, including chest pain or severe chills.
• Immune System Hypersensitivity: The body may develop antibodies against Eculizumab, which could potentially reduce its effectiveness over time.
• Severe Skin Rashes: Including urticaria (hives) or dermatitis.

> Warning: Stop taking Eculizumab and call your doctor immediately or seek emergency care if you experience any of the following:

• Signs of Meningococcal Infection: This is the most critical risk. Symptoms include a high fever, severe headache, stiff neck, nausea, vomiting, confusion, or a rash that does not fade when pressed. This can be fatal if not treated within hours.
• Anaphylaxis (Severe Allergic Reaction): Difficulty breathing, swelling of the face or throat, rapid heart rate, or feeling like you might pass out.
• Signs of Other Serious Infections: Such as a high fever, persistent cough, or painful urination. Eculizumab increases the risk of infections from encapsulated bacteria like Streptococcus pneumoniae and Haemophilus influenzae.
• Hemolysis Recurrence (PNH patients): If you miss a dose, watch for dark-colored urine, extreme tiredness, or shortness of breath.
• Thrombotic Microangiopathy (aHUS patients): If you miss a dose, watch for decreased urine output, swelling, or confusion.

Long-term use of Eculizumab requires ongoing monitoring for secondary infections. Because the medication suppresses a specific part of the immune system indefinitely, patients remain at a baseline higher risk for certain bacterial infections for as long as they are on the drug. There is no evidence currently suggesting that long-term use leads to organ damage; in fact, for many, it prevents organ damage caused by their underlying disease.

Eculizumab carries a Boxed Warning (the FDA’s most serious warning) regarding the risk of serious meningococcal infections.

• Risk: Life-threatening and fatal meningococcal infections (caused by Neisseria meningitidis) have occurred in patients treated with Eculizumab.
• Prevention: Patients must be vaccinated with meningococcal vaccines (both MenACWY and MenB) at least 2 weeks prior to the first dose. If urgent treatment is needed, the patient must receive prophylactic antibiotics during the 2-week window after vaccination.
• REMS Program: Because of this risk, Eculizumab is only available through a restricted program called the Soliris REMS (Risk Evaluation and Mitigation Strategy).

Report any unusual symptoms to your healthcare provider immediately. Early intervention is vital for managing potential complications.

Eculizumab is a powerful immunosuppressant that specifically targets the terminal complement system. While this is necessary to treat conditions like PNH and aHUS, it significantly lowers the body's ability to fight off certain types of bacteria. Patients must be educated on the early signs of infection and must carry a Patient Safety Card at all times to inform other medical professionals (such as ER doctors) that they are taking a complement inhibitor.

WARNING: SERIOUS MENINGOCOCCAL INFECTIONS

Life-threatening and fatal meningococcal infections have occurred in patients treated with Eculizumab. Meningococcal infection may become rapidly life-threatening or fatal if not recognized and treated early.

• Comply with the most current Advisory Committee on Immunization Practices (ACIP) recommendations for meningococcal vaccination in patients receiving a complement inhibitor.
• Immunize patients with meningococcal vaccines at least 2 weeks prior to administering the first dose of Eculizumab and revaccinate according to ACIP recommendations.
• Monitor patients for early signs of meningococcal infection and evaluate immediately if infection is suspected.

• Allergic Reactions / Anaphylaxis: As with any protein-based intravenous medication, there is a risk of severe allergic reactions. Healthcare providers will monitor you closely during and after the infusion.
• Other Infections: Beyond meningococcal risk, Eculizumab increases susceptibility to other encapsulated bacteria, such as Streptococcus pneumoniae and Haemophilus influenzae type b (Hib). Ensure all routine vaccinations are up to date.
• Infusion Reactions: Some patients may experience a drop in blood pressure or respiratory distress during the infusion. The infusion rate may be slowed or stopped if this occurs.
• Monitoring for Disease Activity: If treatment is interrupted or discontinued, there is a high risk of a 'rebound' effect where the underlying disease (like PNH or aHUS) becomes severely active again, leading to life-threatening complications.

Patients on Eculizumab require regular laboratory monitoring to ensure the medication is working and to watch for side effects:

• LDH (Lactate Dehydrogenase): In PNH patients, this is the primary marker used to measure the level of red blood cell destruction.
• Complete Blood Count (CBC): To monitor hemoglobin levels and platelet counts.
• Renal Function Tests: To monitor kidney health, especially in aHUS patients.
• Signs of Infection: Regular clinical assessments for any fever or localized infection.

Eculizumab generally does not affect the ability to drive or operate machinery. However, some patients experience dizziness or fatigue following an infusion. It is recommended to see how the medication affects you before engaging in these activities.

There are no known direct interactions between Eculizumab and alcohol. However, alcohol can sometimes mask symptoms of infection or contribute to headaches, which are already a side effect of the drug. Discuss your alcohol consumption with your doctor.

Stopping Eculizumab is a high-risk event. For PNH patients, discontinuation can lead to massive hemolysis. For aHUS patients, it can lead to sudden kidney failure. If you must stop treatment, your doctor will monitor you intensely for several weeks for signs of disease relapse. Never stop this medication without a direct order and a monitoring plan from your specialist.

> Important: Discuss all your medical conditions, including any history of infections or immune system problems, with your healthcare provider before starting Eculizumab.

There are no drugs that are strictly 'contraindicated' (never to be used) with Eculizumab in the traditional sense of chemical reactivity. However, live vaccines should generally be avoided shortly before or during treatment because the suppressed immune system may not respond correctly to the vaccine, or the vaccine strain could theoretically cause an infection.

• Neonatal Fc Receptor (FcRn) Blockers: Drugs like efgartigimod (used for Myasthenia Gravis) may decrease the levels of Eculizumab in the blood. This is because both drugs interact with the same recycling pathway (the FcRn receptor) that keeps antibodies in circulation longer. If used together, the effectiveness of Eculizumab might be reduced.
• Plasmapheresis / Plasma Exchange (PLEX): These procedures physically remove proteins from the blood. Since Eculizumab is a protein that stays in the blood, PLEX will remove the medication from the body. If you require PLEX, a supplemental dose of Eculizumab is usually required immediately afterward.
• Intravenous Immunoglobulin (IVIG): IVIG can compete with Eculizumab for recycling receptors, potentially lowering the concentration of Eculizumab in the system.

• Other Immunosuppressants: Using Eculizumab with other drugs that suppress the immune system (like corticosteroids, azathioprine, or methotrexate) can further increase the cumulative risk of serious infections. While often necessary, this combination requires vigilant monitoring for signs of illness.

There are no known interactions between Eculizumab and specific foods, including grapefruit, dairy, or caffeine. Because the drug is administered intravenously, it bypasses the digestive system's metabolic pathways.

While there are no documented interactions with herbs like St. John's Wort or Ginkgo Biloba, patients should be cautious. Some supplements can affect blood clotting or immune function. Always inform your doctor of any 'natural' products you are taking, as they could complicate the management of PNH or aHUS.

Eculizumab can interfere with certain laboratory tests:

• Complement Activity Assays: Eculizumab will naturally cause a decrease in 'CH50' levels (a test of total complement activity). This is an expected result of the drug's action and not necessarily a sign of a problem.
• Immunoassays: In rare cases, the presence of the monoclonal antibody in the blood can interfere with certain protein-based lab tests. Always tell the lab technician that you are on a monoclonal antibody therapy.

For each major interaction, the mechanism usually involves either the physical removal of the drug (as in PLEX) or competition for the receptors that keep the drug in the bloodstream. The clinical consequence is typically a reduction in the drug's efficacy, which could lead to a 'breakthrough' of the underlying disease. Management usually involves timing the doses appropriately or providing supplemental doses.

> Important: Tell your doctor about ALL medications, supplements, and herbal products you are taking, including over-the-counter drugs.

There are two primary conditions where Eculizumab must NEVER be used:

1. 1Active Neisseria meningitidis Infection: If a patient has a current, active meningococcal infection, Eculizumab must not be started. Because the drug blocks the body's primary defense against this specific bacteria, giving it during an active infection could lead to rapid death.
2. 2Unvaccinated Patients: Unless the risk of delaying Eculizumab treatment outweighs the risk of developing a meningococcal infection (and the patient is given prophylactic antibiotics), the drug should not be started until the patient is vaccinated. This is a safety mandate under the REMS program.

These are conditions where the doctor must carefully weigh the benefits against the risks:

• Systemic Infections: If a patient has any ongoing serious infection (like pneumonia or sepsis), healthcare providers may delay the start of Eculizumab until the infection is resolved.
• Hypersensitivity to Murine Proteins: Eculizumab is a 'humanized' antibody but contains some components derived from murine (mouse) cell lines. Patients with a known severe allergy to mouse proteins should be treated with extreme caution.
• Pregnancy and Breastfeeding: While not an absolute contraindication, the risks to the fetus or infant must be weighed against the life-threatening risks of the mother's untreated disease.

There is a potential for cross-sensitivity with other complement inhibitors, such as Ravulizumab (Ultomiris). If a patient has had a severe anaphylactic reaction to one complement inhibitor, they may be at a higher risk for a similar reaction to Eculizumab. There is no known cross-sensitivity with common antibiotics or non-protein medications.

> Important: Your healthcare provider will evaluate your complete medical history, including your vaccination status and any current infections, before prescribing Eculizumab.

Eculizumab is categorized as a drug that should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. Data from pregnancy registries suggest that many women with PNH or aHUS have had successful pregnancies while on Eculizumab. However, the drug (an IgG antibody) is known to cross the placenta, especially during the third trimester. There is a theoretical risk of complement suppression in the newborn, although clinical studies have not consistently shown adverse outcomes in infants. Untreated PNH or aHUS during pregnancy carries a very high risk of maternal and fetal death due to blood clots and organ failure.

Limited data suggest that Eculizumab is excreted in human breast milk in very small amounts. However, because it is a large protein, it is likely to be broken down in the infant's digestive system before it can be absorbed into their bloodstream. Most experts believe that the benefits of breastfeeding outweigh the potential risks, but the decision should be made in consultation with a pediatrician.

Eculizumab is FDA-approved for use in children for PNH and aHUS. It has been shown to be effective and generally safe in infants as young as 2 months old for the treatment of aHUS. The primary concern in children is ensuring they are fully vaccinated against N. meningitidis, S. pneumoniae, and H. influenzae type b, as children are naturally more susceptible to these infections.

In clinical trials, patients over the age of 65 did not show significant differences in how they responded to Eculizumab compared to younger patients. However, older adults are generally at a higher risk for infections and may have more underlying heart or lung issues that could make an infusion reaction more serious. No specific dose adjustment is required based solely on age.

Eculizumab is not cleared by the kidneys. Therefore, no dose adjustment is necessary for patients with kidney disease or those on dialysis. In fact, Eculizumab is often used specifically to treat aHUS, a disease that primarily causes kidney damage, and it has been shown to improve or stabilize renal function in those patients.

There are no specific studies of Eculizumab in patients with severe liver disease. However, because monoclonal antibodies are cleared through protein catabolism rather than liver metabolism, hepatic impairment is not expected to change the drug's levels in the body. No dose adjustments are recommended.

> Important: Special populations require individualized medical assessment. Always inform your specialist if you are pregnant, planning to become pregnant, or have other major health conditions.

Eculizumab is a humanized monoclonal IgG2/4k antibody that binds to the C5 complement protein with high affinity. Its molecular target is the terminal portion of the complement cascade. By binding to C5, Eculizumab sterically hinders the cleavage of C5 into C5a (a pro-inflammatory anaphylatoxin) and C5b (the initiator of the Membrane Attack Complex). By preventing the formation of the C5b-9 complex (MAC), Eculizumab prevents the osmotic lysis (bursting) of red blood cells in PNH and the endothelial cell damage in aHUS. This action is highly specific and does not interfere with the 'upstream' complement functions like opsonization (marking bacteria for destruction) or the clearance of immune complexes.

Following the first infusion, Eculizumab provides a rapid and sustained reduction in terminal complement activity. In PNH patients, this is evidenced by a significant drop in LDH levels, usually within the first week of treatment. The drug-to-target ratio is key; enough Eculizumab must be present in the blood to bind all available C5. If the concentration of the drug falls below a certain threshold (typically 50-100 mcg/mL), complement activity may return, leading to 'breakthrough hemolysis.'

| Parameter | Value |

|---|---|

| Bioavailability | 100% (IV administration) |

| Protein Binding | Not applicable (it is a protein) |

| Half-life | 11 to 17 days (Adults with PNH) |

| Tmax | End of infusion |

| Metabolism | Non-CYP; Cellular catabolism |

| Excretion | Not renally or fecally excreted |

• Molecular Formula: C6468H10012N1726O2013S42 (approximate for the protein structure)
• Molecular Weight: Approximately 148,000 Daltons (148 kDa)
• Solubility: Soluble in aqueous buffered solutions
• Structure: A humanized antibody consisting of two 448 amino acid heavy chains and two 214 amino acid light chains. It is produced in a Chinese Hamster Ovary (CHO) cell culture.

Eculizumab is the prototype of the Complement Inhibitor [EPC] class. It is categorized as a selective immunosuppressant. Related medications include Ravulizumab (a longer-acting version of eculizumab) and Pegcetacoplan (which targets C3 instead of C5).