Imfinzi: Uses, Dosage, Side Effects, Mode of Action and More

Imfinzi (pronounced im-FIN-zee) is a type of immunotherapy drug used in cancer treatment and administered as an intravenous infusion. This medicine does not directly kill the cancer cells, but helps your immune system find and attack them. 

Imfinzi (durvalumab) was first approved by the FDA in 2017 for treating locally advanced or metastatic bladder cancer. Since then, it has received approval for treating additional, various types of cancers in adults.  

While Imfinzi improves survival rates, it also carries adverse effects. Read on to understand its usage, recommended dosage, side effects, mechanism of action, and more. 

Important Safety Information

Since Imfinzi helps the immune system fight cancer, it can also cause your immune system to attack healthy tissues or organs, potentially affecting their function. This can lead to severe or even life-threatening problems and may result in death. These problems can happen at any time during treatment or even after it has ended.

Imfinzi: Uses or Indications

Imfinzi is prescribed when the cancer is advanced, has spread, cannot be entirely removed by surgery, or has returned after previous treatment. It is indicated to treat patients with the following types of cancers: 

• Small cell lung cancer (SCLC)
• Non-small cell lung cancer (NSCLC)
• Biliary tract cancer (BTC), which includes cancer of the bile ducts and gallbladder
• Hepatocellular carcinoma (HCC)
• Muscle-invasive bladder cancer (MIBC)
• Endometrial cancer (dMMR)

Imfinzi can be used alone (as a monotherapy) or combined with other immunotherapies (e.g., Imjudo) or chemotherapy, depending on the type of cancer being treated. 

Mechanism of Action (MOA)

Your immune system can recognize and attack the harmful cells, including cancerous ones. However, some cancer cells develop genetic changes and produce a protein called PD-L1 (Programmed Death-Ligand 1). 

This protein (PD-L1) is also present on the surface of healthy cells, which usually acts as a safety signal to prevent the immune system from attacking them. Cancer cells, on the other hand, also start to produce a lot of PD-L1, which allows them to hide from the immune system and keep multiplying. 

Durvalumab, the active ingredient in Imfinzi, is a PD-L1-blocking antibody and belongs to the class of immune checkpoint inhibitors. Durvalumab works by blocking the PD-L1 protein, which helps the immune cells, especially T-cells, to find, recognize, and attack cancer cells. 

Dosage Form and Administration

Imfinzi is available as a liquid solution in single-dose vials. Each vial contains 50 mg/ml of Imfinzi solution. The single-dose vials come in two sizes: 

• 120 mg/2.4 ml
• 500 mg/10 ml

The medication is administered as an IV infusion by a healthcare professional. With IV infusions, the drug is slowly injected into a vein over a certain period of time. Imfinzi infusion typically takes 1 hour to complete.

Recommended Dosage for Cancer Patients

The dosage of Imfinzi (Durvalumab) depends on the type of cancer being treated, the patient’s body weight (kg), and whether this medication is given alone or combined with other therapies. 

The following are the recommended dosages of Imfinzi for adult patients with certain types of cancers. 

1. Imfinzi Dosage for Non-Small Cell Lung Cancer (NSCLC)

The dosage of Imfinzi is prescribed based on whether the NSCLC is unresectable (cannot be removed surgically) or metastatic (spread to other parts of the body). Imfinzi is administered with other cancer treatments with varying dosages and frequencies. 

However, the dose typically prescribed for non-small cell lung cancer is an infusion of 10 mg/kg every 2 weeks or 1,500 mg every 4 weeks (if you weigh ≥ 30 kg). If you weigh < 30 kg, a dose of 10 mg/kg will be given every 2 weeks. 

2. Imfinzi Dosage for Small Cell Lung Cancer (SCLC)

To treat limited-stage SCLC, you will receive Imfinzi as a single agent once every 4 weeks.

• If your weight is ≥ 30 kg, a 1,500 mg dose is administered.
• If your weight is < 30 kg, you’ll receive 20 mg/kg.

For extensive-stage SCLC, you’ll receive your first dose of Imfinzi with chemotherapy for cycles 1 through 4, then as a single agent (Imfinzi alone). 

• If your weight is ≥ 30 kg, an infusion of 1,500 mg/kg is administered once every 3 weeks. After cycles 1 through 4, you’ll receive 1,500 mg of Imfinzi alone every 4 weeks.
• If your weight is < 30 kg, a dose of 20 mg/kg is given. After cycles 1 through 4, you’ll receive 10 mg/kg once every 2 weeks.

3. Imfinzi Dosage for Biliary Tract Cancer (BTC)

For biliary tract cancer, Imfinzi is given with chemotherapy once every 3 weeks for up to 8 cycles. After finishing chemotherapy, you’ll receive a dose of Imfinzi as a standalone treatment every 4 weeks.

• If you weigh ≥ 30 kg, an infusion of 1,500 mg/kg is given, while an infusion of 20 mg/kg is given if you weigh < 30 kg.

4. Imfinzi Dosage for Hepatocellular Carcinoma

To treat unresectable hepatocellular carcinoma (HCC), a type of liver cancer that cannot be surgically removed, you’ll receive the first dose of Imfinzi in combination with immunotherapy (tremelimumab). 

After immunotherapy, it is administered as a single agent once every 4 weeks. An infusion of 1,500 mg/kg will be given if the weight is ≥ 30 kg, and 20 mg/kg in cases of < 30 kg. 

5. Imfinzi Dosage for Endometrial Cancer (dMMR)

To treat advanced or recurrent endometrial cancer, you’ll receive an Imfinzi dose combined with other cancer medicines every 3 weeks for six treatment cycles, then Imfinzi alone. 

• If you weigh ≥ 30 kg, you’ll receive a dose of 1,120 mg/ kg once every 3 weeks for six cycles. After that, your dosage will be changed to 1,500 mg Imfinzi once every 4 weeks as a stand-alone treatment.
• If you weigh < 30 kg, you’ll receive a dose of 15 mg/kg once every 3 weeks for six cycles. After that, your dosage will be changed to 20 mg/kg Imfinzi once every 4 weeks as a stand-alone treatment. 

For more information about your specific dosage, talk with your doctor.

Side Effects

You may experience some of the common side effects during treatment with Imfinzi. Note that these side effects can vary depending on the type of cancer you have and other cancer medicines you may be using.  

If you’re taking Imfinzi alone, you may experience the following effects: 

• Cough
• Diarrhea or constipation
• Rash
• Joint Pain
• Fever
• Abdominal (stomach) pain
• Infection in the nose and throat
• Itching
• Hypothyroidism 
• Anemia (low hemoglobin level)
• Nausea or vomiting
• Shortness of breath
• Hair loss
• Low appetite
• Lung inflammation (pneumonitis)
• Low magnesium, elevated liver enzymes (AST/ALT)

Though less common, Imfinzi can also cause serious effects like: 

• Severe allergic reactions, which include fever, swollen lymph nodes, swelling in the face, lips, tongue, or throat, itching, skin rash, and breathing problems 
• Infusion-site reactions such as fever or chills, flushing, shortness of breath, itching or skin rash, dizziness, or fainting
• Immune system reactions, which include:
  • Pneumonitis (inflamed lungs)
  • Colitis (inflamed intestine)
  • Hepatitis (inflamed liver)
  • Inflamed nerves
  • Inflamed muscles or joints
  • Heart or blood vessel inflammation
  • Inflamed eye (Uveitis)
  • Inflamed brain (encephalitis)
  • Inflamed kidney (nephritis)
  • Inflammation in the hormonal glands

Tell your healthcare provider right away if you have any of these signs or symptoms, even if you are no longer taking this medicine.

Information to Tell Your Doctor Before Taking Imfinzi

Tell your doctor if you have/are:

• Autoimmune disorders like Crohn’s disease, ulcerative colitis, or lupus
• Received an organ transplant 
• Received radiation treatment for your chest area
• Received or plan to receive a stem cell transplant that uses donor stem cells (allogeneic)
• Received radiation treatment to the chest area
• A condition that affects your nervous system, such as myasthenia gravis or Guillain-Barré syndrome
• Pregnant or plan to become pregnant, as Imfinzi can harm your unborn baby
• Are breastfeeding or plan to breastfeed. It is not known if Imfinzi passes into your breast milk. (Do not breastfeed during treatment and for 3 months after the last dose of Imfinzi).
• Taking any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements.