Ecallantide - Uses, Mechanism of Action, Precautions, and Side Effects

Overview:

Ecallantide is a potent human plasma kallikrein inhibitor used to treat hereditary angioedema (HAE). This recombinant protein blocks kallikrein, which triggers inflammatory pathways and excess bradykinin production, causing severe swelling in HAE patients. Ecallantide's high-affinity inhibition effectively alleviates symptoms when administered as a subcutaneous injection. Additionally, it has been used off-label for nonhistaminergic angioedema management. This innovative treatment offers new hope for managing this rare genetic disorder.

How Does Ecallantide Work?

Angioedema attacks in individuals with C1-INH deficiency are caused by the excessive release of a substance called bradykinin, which affects blood vessels. The release of bradykinin is triggered by the uncontrolled activation of a protein called factor XII, leading to the formation of factor XIIa and kallikrein. C1-INH normally inhibits both factor XIIa and kallikrein. However, kallikrein can further activate factor XII and release more bradykinin.

The specific trigger for the initial activation of plasma kallikrein in the body is currently unknown. But when it is activated, it cleaves high-molecular-weight kininogen (HMWK) and releases more bradykinin. Bradykinin then acts on blood vessels, increasing their permeability and causing fluid to leak into tissues, resulting in the characteristic symptoms of HAE attacks.

Ecallantide, the medication used to treat HAE, acts on the kinin pathway by blocking plasma kallikrein. Doing so effectively reduces the excessive release of bradykinin, providing rapid and reversible relief from HAE symptoms.

What Is the Dosage of Ecallantide?

• Ecallantide is available as a clear, sterile solution in vials containing 10 mg (milligram) of Ecallantide as the active substance.

• The recommended initial dose is 30 mg (3.0 mL), administered subcutaneously (under the skin) in three separate 10 mg doses.

• Injection sites should be far away from the site of the angioedema (tissue swelling and fluid buildup).

• Each 30 mg dose is supplied in three vials, with each vial containing 1 mL (milliliter) of 10 mg/mL of Ecallantide.

How Effective Is Ecallantide?

Ecallantide is effective in relieving symptoms, reducing the severity of attacks, and shortening the duration of attacks in people with hereditary angioedema. Regarding safety and tolerability, Ecallantide was generally well-tolerated by patients with HAE attacks in clinical trials. Most adverse events were mild to moderate in severity, and no event that was more common in Ecallantide than in placebo recipients occurred in more than ten percent of patients. The most clinically relevant treatment-emergent adverse event (TEAE) was hypersensitivity to Ecallantide, which occurred in 13 patients during the clinical studies. However, most of these hypersensitivity symptoms resolved either spontaneously or following treatment.

For Patients:

What Is Hereditary Angioedema?

Hereditary angioedema is a form of autosomal dominant disease characterized by repeated bouts of severe swelling. This condition is known as angioedema. The disease is caused by a deficiency in the C1-inhibitor protein or a disruption in its action. HAE can impact the upper airway, skin, digestive system, limbs, and face, among other body areas.

Each person has a unique set of HAE symptoms. Even though slight trauma or stress can occasionally provoke an episode, swelling can sometimes happen on its own without any identified triggers. When the intestinal tract is affected, people may feel extremely sick and have severe abdominal discomfort. Breathing issues and perhaps fatal airway obstruction can result from swelling in the airway. During an attack, some HAE patients may have a non-itchy rash known as erythema marginatum.

HAE is a chronic disorder that develops at birth. Even though symptoms frequently start in childhood and get worse during adolescence, many people are unaware that HAE is responsible for their edema until they are adults. Individuals differ significantly in terms of the attacks' frequency, severity, and location. Although the swelling typically goes away independently, it can occasionally be a serious emergency, especially when the throat swells and restricts the airways.

HAE can now be treated more effectively, and continuing research is looking for novel ways to control the condition. People with HAE must collaborate with a multidisciplinary healthcare team to assess and manage their illnesses properly.

What Are the Things to Inform the Doctor Before Taking Ecallantide?

• It is critical to inform the doctor about any allergies the patient may have before using Ecallantide.

• Caretakers should be informed about the patient's allergies in case of an emergency.

• Follow-up physicians must be informed about the prior administration of Ecallantide.

• The patient's pregnancy or lactation status should be communicated to caregivers or physicians.

• Ecallantide should only be taken under a doctor's prescription and with medical supervision.

• Since the medicine is available in injection form, patients should not self-administer it.

What Are the Side Effects of Ecallantide?

The side effects of Ecallantide can be categorized as follows:

Less common side effects (may require immediate medical attention):

• Blurred vision.

• Chest discomfort.

• Confusion.

• Cough.

• Difficulty with breathing.

• Difficulty with swallowing.

• Lightheadedness, faintness, or dizziness after abruptly standing up from a seated or lying position.

• Fast heartbeat.

• The feeling of warmth.

• Fever.

• Hives or welts, itching, or skin rash.

• Puffiness or edema surrounding the eyes, lips, tongue, or eyelids.

• Redness of the face, neck, arms, and occasionally upper chest are red.

• Redness of the skin.

• Runny nose.

• Sneezing.

• Stuffy nose.

• Sweating.

• Throat irritation.

• Tightness in the chest.

• Unusual tiredness or weakness.

Less common side effects (usually do not need medical attention but may be bothersome):

• Headache.

• Injection site reactions (bruising, itching, redness, skin swelling, pain, rash, or irritation).

• Muscle aches.

• Nausea.

• Sore throat.

• Diarrhea.

• Tired feeling.

Serious side effects (requiring immediate medical attention):

• Hives.

• Difficulty breathing.

• Swelling of the face, lips, tongue, or throat.

• Chest pain or tightness.

• Fast or weak heartbeat.

• Wheezing.

• Cough.

• Throat irritation.

• Hoarse voice.

• Tight feeling in the throat.

• Itching.

• Rash.

• Flushing (warmth, redness, or tingly feeling).

Furthermore, severe side effects need to be treated right away, like tremors, a high fever, profuse sweating, confusion, slurred speech, arm or leg weakness, walking difficulties, loss of coordination, and extremely stiff muscles. These symptoms are important to watch for, and medical help should be sought if experienced while using Ecallantide.

For Doctors:

Indication:

Ecallantide is indicated for the treatment of acute attacks of hereditary angioedema (HAE) in patients who are 12 years of age and older. It treats sudden episodes of HAE and provides symptomatic relief during these acute attacks. Therefore, doctors can consider prescribing Ecallantide to eligible patients who experience acute episodes of HAE to alleviate their symptoms.

Dose:

For the treatment of acute attacks of hereditary angioedema (HAE) in patients aged 12 years and older:

• Administer 30 mg (3 milliliters) of Ecallantide subcutaneously (SC).

• The 30 mg dose is divided into three separate 10 mg (1 milliliter) injections.

• A second dose of 30 mg may be given within 24 hours if the attack does not go away.

The safety and efficacy of Ecallantide have not been established for patients below 12 years of age.

What Are the Pharmacological Aspects of Ecallantide?

Pharmacodynamics:

The pharmacodynamics of Ecallantide can be summarized as follows:

• Intravenous administration of Ecallantide doses equal to or higher than 20 mg/m^2 (body surface area or BSA) resulted in a prolonged activated partial thromboplastin time (aPTT), indicating an effect on the intrinsic coagulation pathway. However, there were no indications of bleeding associated with this prolongation.

• Ecallantide administration has been associated with instances of arrhythmia.

• In clinical trials, Ecallantide demonstrated a significant improvement in symptoms affecting the oropharynx, abdomen, gastrointestinal tract, and limbs within four hours after intravenous administration compared to placebo. It also showed a substantial decrease in the severity and duration of attacks in patients with moderate-to-severe hereditary angioedema (HAE) attacks.

• Ecallantide had no significant effect on the QTc interval, heart rate, or any other electrocardiogram (ECG) components.

• No known exposure-response links exist between Ecallantide and parts of the complement or kallikrein-kinin pathways.

• In a clinical trial, the subcutaneous administration of 30 mg of Ecallantide showed no significant QT prolongation, heart rate changes, or other ECG abnormalities compared to placebo.

Mechanism of Action:

Ecallantide is a strong, specific, and reversible plasma kallikrein inhibitor, a key component of the kallikrein-kinin system. The kallikrein-kinin system is a proteolytic cascade that has a role in the inflammation and coagulation pathways.

Hereditary angioedema is characterized by insufficiency or dysfunction of the C1-esterase inhibitor (C1-INH), a key endogenous inhibitor of plasma kallikrein. This deficiency leads to uncontrolled activity of plasma kallikrein and excessive synthesis of bradykinin, a vasoactive mediator that increases vascular permeability and promotes regional swelling, inflammation, and discomfort.

When Ecallantide binds to plasma kallikrein, it blocks the enzyme's active site, preventing high molecular weight (HMW) kininogen from converting to bradykinin. Ecallantide decreases the synthesis of bradykinin and attenuates its activities by specifically inhibiting plasma kallikrein. In turn, this lessens vascular permeability and the symptoms that characterize acute HAE attacks. Because Ecallantide has an inhibitory constant (Ki) of 25 pM, it has a strong affinity for plasma kallikrein.

Pharmacokinetics:

After the administration of a single 30 mg subcutaneous dose of Ecallantide:

• The maximum plasma concentration (Cmax) of Ecallantide is observed approximately two to three hours post-dose and has a mean value of 586 ± 106 ng/mL.

• The mean area under the concentration-time curve (AUC) is 3017 ± 402 ng/hr/mL, indicating the overall exposure to Ecallantide.

• Ecallantide plasma concentration declines with a mean elimination half-life of 2.0 ± 0.5 hours, representing the time it takes for half of the drug to be cleared from the plasma.

• The plasma clearance of Ecallantide is 153 ± 20 mL/min, indicating the rate at which the drug is cleared from the plasma.

• The volume of distribution of Ecallantide is 26.4 ± 7.8 L, which represents the apparent volume into which the drug distributes throughout the body.

• Based on population pharmacokinetic analysis, factors such as body weight, age, and gender do not significantly affect Ecallantide exposure.

• Ecallantide has a molecular weight of 7054 Da and is a small protein.

• The renal elimination of Ecallantide in the urine of treated subjects has been demonstrated.

• There is no pharmacokinetic data available for individuals or subjects that have either hepatic or renal impairment.

Toxicity:

• Overdose: Ecallantide overdoses have not been reported. Patients diagnosed with hereditary angioedema have been given single doses of up to 90 mg intravenously, and there has been no evidence of any dose-related harm.

• Carcinogenic or Mutagenic Effect: Ecallantide has not been the subject of any investigations on humans or animals to determine whether it is carcinogenic or mutagenic.

• Impact on Fertility and Reproductive Function: Ecallantide doses up to 25 mg/kg/day in rats, which is roughly 2.7 times the maximum dose that is advised for humans on the BSA (mg/m2) basis, did not appear to have a noticeable impact on fertility or reproductive performance.

• Lethal Dose: The approximate lethal dose of Ecallantide was determined to be 25 mg/kg intravenously for rats and 5 mg/kg intravenously for rabbits.

• Rat Carcinogenic Potential: A two-year rat research found no evidence of tumorigenicity at Ecallantide dosages up to 10 mg/kg given subcutaneously every three days (about two times the maximum dose for humans considered safe based on AUC).

What Are the Contraindications of Ecallantide?

Do not administer Ecallantide to a patient who has a known clinical hypersensitivity to Ecallantide.

Warnings and Precautions:

• Anaphylaxis: Ecallantide may result in a potentially fatal allergic reaction known as anaphylaxis, which is a significant allergic reaction. If the patient experiences any anaphylactic symptoms after getting the injection, they need to seek emergency medical help right once. Cough, swallowing problems, dizziness, rapid heartbeat, wheezing, shortness of breath, difficulty breathing, chest tightness, swelling of the face, hands, tongue, or throat, fever, chills, runny nose or sneezing, itching or hives, and lightheadedness or faintness may be among these symptoms.

• Hypersensitivity Reactions: Patients on Ecallantide have experienced potentially dangerous hypersensitivity reactions, such as anaphylaxis (severe allergic reaction). These reactions may be associated with flushing, pharyngeal edema, pruritus, rhinorrhea, sneezing, nasal congestion, throat irritation, urticaria, wheezing, and hypotension. After administration, patients should be monitored for sufficient time, considering the clinical trial data on the start of anaphylaxis. Due to the similarities in symptoms between acute hereditary angioedema (HAE) symptoms and those of hypersensitivity responses, close monitoring is crucial.

• Ecallantide should not be given to patients who are known to be clinically hypersensitive to the drug. Additional dosages should not be given to those who have previously experienced Ecallantide hypersensitivity.

• A healthcare practitioner should administer Ecallantide along with the necessary medical assistance to control anaphylaxis and hereditary angioedema.

• Patients need to be made aware of the possibility of anaphylaxis and other hypersensitive reactions when taking Ecallantide.

• Doctors should closely monitor patients taking Ecallantide for effectiveness and the occurrence of hypersensitivity events, and they should have access to the right medical care in the event of anaphylaxis.

What Are the Drug Interactions of Ecallantide?

No studies are available to interpret the drug interactions of Ecallantide.

Clinical Studies:

The efficacy of Ecallantide was evaluated in two randomized, double-blind, placebo-controlled trials (EDEMA3 and EDEMA4) involving a total of 168 patients with HAE-C1-INH.

Ecallantide showed significant improvements in both trials compared to placebo at four hours and 24 hours after dosing, as assessed by the mean symptom somplex Severity (MSCS) score and the treatment outcome score (TOS). At four hours, the median TOS was 50.0 for the Ecallantide-treated group and 0.0 for the placebo group, indicating a significant improvement in symptoms with Ecallantide. At 24 hours, the median TOS was 75.0 for the Ecallantide group and 0.0 for the placebo group.

The median change in the MSCS score at four hours was −1.00 in the Ecallantide group and −0.50 in the placebo group. At 24 hours, the median change in the MSCS score was −1.00 with Ecallantide and −0.50 with placebo. These results demonstrate that Ecallantide effectively reduces the severity of HAE attacks and leads to sustained improvements in symptoms.

Additionally, in the EDEMA4 trial, patients treated with ecallantide showed a greater decrease in MSCS score compared to baseline and a higher TOS than placebo-treated patients, and these differences were statistically significant.

The EDEMA4 Trial:

• The EDEMA4 trial included 96 individuals with hereditary angioedema who were experiencing acute attacks. It was a double-blind, randomized, placebo-controlled study.

• The primary goal was the change from baseline in Mean Symptom Complex Severity (MSCS) score at four hours, while a key secondary endpoint was the Treatment Outcome Score (TOS) at four hours.

• Compared to placebo, patients treated with Ecallantide had a bigger decrease in MSCS score and a higher TOS. These differences were statistically significant.

• Ecallantide-treated patients also had a bigger decline in MSCS score and a higher TOS at 24 hours compared to placebo.

• Compared to Ecallantide-treated individuals, more placebo-treated patients sought medical intervention within 24 hours to manage persistent symptoms.

The EDEMA3 Trial:

• The EDEMA3 trial included 72 individuals with HAE who were having acute attacks. The trial was a randomized, double-blind, placebo-controlled trial.

• The primary outcome was the TOS at four hours, while a key secondary endpoint was the change from baseline in the MSCS at four hours.

• Patients treated with Ecallantide, like EDEMA4, had a bigger decrease in MSCS score and a higher TOS compared to placebo, and these differences were statistically significant.

• Furthermore, compared to Ecallantide-treated patients, more placebo-treated patients required medical intervention to manage unresolved symptoms within 24 hours.

In summary, the clinical studies showed that treatment with Ecallantide significantly improved symptom severity and patient response to treatment compared to placebo in patients with acute attacks of HAE. The efficacy of Ecallantide was assessed using patient-reported outcome measures, including the MSCS score and TOS.