Imfinzi (durvalumab) is a cancer immunotherapy drug approved to treat several types of cancer, including lung cancer, liver cancer, bile duct cancer, endometrial cancer, and bladder cancer. It works by helping your immune system recognize and attack cancer cells that would otherwise evade detection. Made by AstraZeneca, it’s given as an intravenous infusion and is one of a growing class of drugs called checkpoint inhibitors.
How Imfinzi Works
Cancer cells often survive by producing a protein called PD-L1 on their surface. This protein acts like a disguise, binding to receptors on your immune cells (T cells) and essentially telling them to stand down. Your T cells stop attacking, stop multiplying, and stop producing the chemical signals they’d normally use to fight the tumor.
Imfinzi is an antibody that attaches to PD-L1 and blocks it from connecting with your T cells. Once that disguise is stripped away, your immune system can recognize the cancer again and resume its attack. Unlike some older cancer treatments, Imfinzi doesn’t kill cancer cells directly. It removes the brakes that cancer has put on your immune system.
All FDA-Approved Uses
Imfinzi has accumulated a broad range of approvals across multiple cancer types. Some of these uses involve Imfinzi alone, while others pair it with chemotherapy or a second immunotherapy drug called tremelimumab. Here’s the full list of current FDA-approved indications:
- Unresectable stage III non-small cell lung cancer (NSCLC), for patients whose cancer hasn’t progressed after initial chemotherapy and radiation
- Resectable NSCLC, given both before and after surgery alongside chemotherapy
- Metastatic NSCLC, in combination with tremelimumab and platinum-based chemotherapy
- Limited-stage small cell lung cancer (LS-SCLC), for patients whose disease hasn’t progressed after chemotherapy and radiation
- Extensive-stage small cell lung cancer (ES-SCLC), in combination with chemotherapy
- Biliary tract cancer (bile duct and gallbladder cancers), combined with gemcitabine and cisplatin chemotherapy
- Unresectable liver cancer (hepatocellular carcinoma), given with a single dose of tremelimumab
- Mismatch repair deficient endometrial cancer, combined with chemotherapy
- Muscle-invasive bladder cancer, given before and after surgery
Lung Cancer: The Most Established Use
Imfinzi’s best-known role is in stage III non-small cell lung cancer that can’t be removed with surgery. This was its landmark approval, based on the PACIFIC trial, one of the largest studies of its kind. Patients who received Imfinzi after completing chemotherapy and radiation had a five-year overall survival rate of 42.9%, compared to 33.4% for patients who received a placebo. Five-year progression-free survival was 33.1% versus 19.0%. For a cancer stage where long-term survival was historically poor, those numbers represented a meaningful shift.
In December 2024, the FDA expanded Imfinzi’s lung cancer approvals to include limited-stage small cell lung cancer, a particularly aggressive form of the disease. This approval covers patients whose cancer hasn’t worsened after concurrent chemotherapy and radiation. Imfinzi is also approved for extensive-stage small cell lung cancer in combination with chemotherapy, and for metastatic NSCLC when paired with tremelimumab and chemotherapy.
Biliary Tract and Liver Cancer
For biliary tract cancers, which include cancers of the bile ducts and gallbladder, Imfinzi is used alongside two chemotherapy drugs (gemcitabine and cisplatin) as a first-line treatment. The approval was based on a trial of 685 patients with locally advanced or metastatic disease who hadn’t previously received systemic treatment. Patients receive Imfinzi with chemotherapy for up to eight cycles, then continue on Imfinzi alone until the cancer progresses or side effects become unacceptable.
For unresectable liver cancer (hepatocellular carcinoma), Imfinzi takes a different approach. It’s paired with a single upfront dose of tremelimumab, a drug that targets a different immune checkpoint. After that initial combination dose, patients continue with Imfinzi alone every four weeks.
Endometrial Cancer
In June 2024, the FDA approved Imfinzi for primary advanced or recurrent endometrial cancer that is mismatch repair deficient (dMMR). Mismatch repair deficiency means the cancer cells have trouble fixing errors in their DNA, which tends to make them more visible to the immune system and more responsive to immunotherapy. In the clinical trial, patients with dMMR tumors who received Imfinzi with chemotherapy had dramatically better outcomes: median progression-free survival wasn’t even reached in the Imfinzi group, compared to 7 months with chemotherapy alone. The risk of disease progression was reduced by 58%.
Bladder Cancer
Imfinzi is approved for muscle-invasive bladder cancer as both a neoadjuvant and adjuvant treatment, meaning it’s given before surgery (four cycles over about 12 weeks) and then again after surgery (up to eight cycles). This approach aims to shrink the tumor before it’s removed and then reduce the chance of recurrence afterward.
What Treatment Looks Like
Imfinzi is given as an IV infusion lasting about 60 minutes. For most indications, the standard dose for adults weighing 30 kg (about 66 pounds) or more is a flat 1,500 mg. The frequency depends on the cancer type and phase of treatment, but most schedules involve infusions every three or four weeks. Some treatment plans start with more frequent dosing during an initial phase alongside chemotherapy, then shift to a maintenance schedule of Imfinzi alone every four weeks.
Treatment continues until the cancer progresses or side effects become too severe. For some indications, like the adjuvant phase after surgery, there’s a set number of cycles (for example, up to 12 cycles after NSCLC surgery).
Side Effects
Because Imfinzi works by activating your immune system, its side effects are largely driven by that same immune activation turning against healthy tissues. These are called immune-related adverse events, and they can affect nearly any organ.
Skin reactions are the most common side effects across checkpoint inhibitors as a class, including rash and itching, reported in up to 71.5% of patients. Most are mild. Severe skin reactions (grade 3 or higher) occur in 3% or fewer patients on single-agent therapy.
Lung inflammation (pneumonitis) is a particular concern with PD-L1 inhibitors like Imfinzi. The overall incidence is about 2.7% based on a meta-analysis of PD-1/PD-L1 inhibitor studies, though individual trial rates range from 0% to 10%. This is one of the more serious potential side effects and requires prompt attention if you develop a new or worsening cough, chest pain, or shortness of breath during treatment.
Diarrhea and colitis (inflammation of the colon) also occur, though they’re more common and more severe with combination immunotherapy than with Imfinzi alone. Other immune-related side effects can involve the thyroid, liver, kidneys, and other organs. Most are manageable when caught early, which is why regular blood work and monitoring are a standard part of treatment with Imfinzi.