BESPONSA (Inotuzumab Ozogamicin)

What Is BESPONSA and What Is It Used For?

Quick answer: BESPONSA (inotuzumab ozogamicin) is a targeted cancer medicine classified as an antibody-drug conjugate (ADC). It is approved for treating adults with relapsed or refractory B-cell precursor acute lymphoblastic leukemia (ALL), a type of blood cancer characterized by the overproduction of abnormal white blood cells. BESPONSA is used when prior chemotherapy regimens have failed.

Acute lymphoblastic leukemia (ALL) is an aggressive form of blood cancer that arises from the uncontrolled growth of immature lymphocyte precursor cells in the bone marrow. In adults, ALL is relatively uncommon, accounting for approximately 20% of adult leukemias, but it carries a poor prognosis when it relapses after initial treatment or proves refractory (resistant) to standard chemotherapy. B-cell precursor ALL, the specific subtype targeted by BESPONSA, accounts for roughly 75% of adult ALL cases and is characterized by expression of the CD22 surface antigen on leukemia cells.

BESPONSA represents a significant advancement in the treatment of relapsed or refractory B-cell ALL. The active substance, inotuzumab ozogamicin, belongs to a class of medicines called antineoplastic agents — drugs that combat cancer cells. More specifically, it is an antibody-drug conjugate, meaning it combines a monoclonal antibody with a potent cytotoxic (cell-killing) chemical agent. The antibody component is a humanized immunoglobulin G4 (IgG4) antibody that specifically recognizes and binds to the CD22 protein found on the surface of B-cell ALL cells. The cytotoxic component is N-acetyl-gamma-calicheamicin dimethylhydrazide, a powerful DNA-damaging agent derived from the calicheamicin family of antibiotics.

Mechanism of Action

The mechanism of action of BESPONSA is elegantly targeted. When administered intravenously, the antibody-drug conjugate circulates in the bloodstream and seeks out cells expressing the CD22 protein on their surface. CD22 is a cell-surface glycoprotein found predominantly on B-lineage lymphoid cells, making it an ideal target for B-cell ALL therapy. Once the antibody portion of BESPONSA binds to CD22 on the surface of leukemia cells, the entire conjugate is internalized — drawn inside the cell through a process called receptor-mediated endocytosis.

Inside the leukemia cell, the calicheamicin payload is released from the antibody. Calicheamicin then migrates to the cell nucleus, where it binds to the minor groove of DNA and causes double-strand DNA breaks. These irreparable breaks in the genetic material trigger programmed cell death (apoptosis), effectively destroying the leukemia cell. This targeted approach allows BESPONSA to deliver its cytotoxic payload directly to cancer cells while relatively sparing healthy cells that do not express CD22, although some off-target effects can occur since CD22 is also present on normal mature B cells.

Clinical Evidence and Approval

BESPONSA received marketing authorization from the European Medicines Agency (EMA) in June 2017 and approval from the U.S. Food and Drug Administration (FDA) in August 2017. The pivotal clinical trial supporting approval was the INO-VATE ALL study (Study INST 1022), a phase 3, randomized, open-label trial comparing inotuzumab ozogamicin to standard-of-care chemotherapy in 326 adults with relapsed or refractory B-cell precursor ALL. The study demonstrated statistically significant improvements in complete remission rate (80.7% vs 29.4%) and progression-free survival (median 5.0 months vs 1.8 months) compared to standard chemotherapy. BESPONSA also showed improvement in overall survival, with median overall survival of 7.7 months versus 6.7 months.

The drug has been included in major clinical practice guidelines, including those from the National Comprehensive Cancer Network (NCCN) and the European Society for Medical Oncology (ESMO), as a recommended treatment option for adults with relapsed or refractory B-cell precursor ALL. Its role as a bridge to hematopoietic stem cell transplantation has been particularly noted, as achieving complete remission is a prerequisite for successful transplantation.

What Should You Know Before Taking BESPONSA?

Quick answer: Before receiving BESPONSA, you must inform your healthcare team about any liver problems, history of veno-occlusive disease, current infections, or heart rhythm abnormalities. BESPONSA is contraindicated in patients with prior severe VOD, serious ongoing liver disease, or known hypersensitivity to the drug. Women must not become pregnant during treatment, and effective contraception is required for both sexes.

Contraindications

BESPONSA must not be used in certain circumstances. You should not receive this medicine if you:

• Are allergic to inotuzumab ozogamicin or any of the excipients (sucrose, polysorbate 80, sodium chloride, or tromethamine)
• Have had prior confirmed severe hepatic veno-occlusive disease (VOD), also known as sinusoidal obstruction syndrome (SOS) — a condition where blood vessels in the liver become damaged and blocked by blood clots
• Have ongoing severe liver disease, including cirrhosis (scarring of the liver that impairs its function due to long-term damage), nodular regenerative hyperplasia (a condition with signs of elevated blood pressure in the portal vein of the liver), or active hepatitis (inflammation of the liver)

Warnings and Precautions

Before receiving BESPONSA, tell your healthcare provider if any of the following apply to you:

• Liver problems: If you have a history of liver problems or liver disease, or if you show symptoms of hepatic veno-occlusive disease, inform your doctor immediately. VOD may occur during BESPONSA treatment or after subsequent stem cell transplantation.
• Low blood counts: If you experience signs of low blood cell counts, including neutrophils (sometimes accompanied by fever), red blood cells, white blood cells, lymphocytes, or platelets. Symptoms may include susceptibility to infections, fever, bruising easily, or frequent nosebleeds.
• Infusion reactions: If you develop symptoms such as fever, chills, or breathing difficulties during or shortly after a BESPONSA infusion.
• Tumor lysis syndrome: This condition can cause symptoms affecting the stomach and intestines (nausea, vomiting, diarrhea), heart (altered heart rhythm), kidneys (decreased urine output, blood in urine), and nerves and muscles (muscle spasms, weakness, cramps) during or shortly after infusion.
• QT prolongation: If you have a history of or tendency toward prolonged QT interval (a change in the heart's electrical activity that can cause serious irregular heartbeats), are taking medications known to prolong the QT interval, or have abnormal electrolyte levels (calcium, magnesium, potassium).
• Elevated pancreatic enzymes: If you have increased levels of amylase or lipase in your blood, which may indicate problems with the pancreas, liver, gallbladder, or bile ducts.

Your doctor will perform regular blood tests throughout your treatment with BESPONSA to monitor your blood counts, liver function, and electrolyte levels. An electrocardiogram (ECG) will be taken before the first dose and repeated during treatment to check for QT prolongation. During treatment, particularly in the first few days after starting, your white blood cell count may drop significantly (neutropenia), which may be accompanied by fever (febrile neutropenia). You may also develop elevated liver enzymes.

Pregnancy, Breastfeeding, and Fertility

BESPONSA can potentially harm an unborn baby based on its mechanism of action. The following precautions are essential:

• Contraception: Women of childbearing potential must use effective contraception during treatment and for at least 8 months after the last dose. Men must use effective contraception during treatment and for at least 5 months after the last dose.
• Pregnancy: The effects of BESPONSA on pregnant women are unknown, but the drug could harm a fetus. Do not use BESPONSA during pregnancy unless your doctor determines the potential benefit justifies the potential risk. Contact your doctor immediately if you or your partner becomes pregnant during treatment.
• Fertility: Both men and women should seek counseling about fertility preservation measures before starting treatment.
• Breastfeeding: You must stop breastfeeding during treatment and for at least 2 months after the last dose.

Use in Children and Adolescents

BESPONSA is not approved for use in children and adolescents under 18 years of age. Limited clinical data are available for this patient population. Pediatric patients with relapsed or refractory B-cell ALL should discuss appropriate alternative treatment options with their pediatric oncologist.

Driving and Operating Machinery

If you experience unusual tiredness (fatigue is a very common side effect of BESPONSA), you should not drive vehicles or operate machinery. Fatigue can impair your ability to react quickly and safely.

How Does BESPONSA Interact with Other Drugs?

Quick answer: BESPONSA may interact with QT-prolonging medications and hepatotoxic agents. Tell your healthcare provider about all medications you are taking, including prescription drugs, over-the-counter medicines, and herbal supplements. No formal drug-drug interaction studies have been conducted, but caution is warranted with concomitant use of known hepatotoxic agents and drugs that prolong the QT interval.

While no formal drug-drug interaction studies have been conducted with inotuzumab ozogamicin, potential interactions should be considered based on the known pharmacological properties and safety profile of BESPONSA. The drug is primarily metabolized through non-enzymatic reduction of the calicheamicin disulfide bond and is not expected to be significantly affected by cytochrome P450 (CYP) enzyme inhibitors or inducers. However, certain drug combinations require special attention due to overlapping toxicity profiles.

Major Interactions

Minor Interactions

The following interactions are generally manageable with appropriate monitoring but should still be discussed with your healthcare team:

• Anticoagulants and antiplatelet agents: Given BESPONSA's association with thrombocytopenia, concurrent use of blood-thinning medications may increase bleeding risk. Platelet counts should be closely monitored.
• CYP3A4 substrates: While inotuzumab ozogamicin itself is not significantly metabolized by CYP enzymes, the calicheamicin component may have minor interactions with CYP3A4 substrates. Clinical significance is considered low.
• Electrolyte-altering medications (diuretics, laxatives): Drugs that can lower potassium, magnesium, or calcium levels may increase the risk of QT prolongation. Electrolyte monitoring is recommended.

Always inform your healthcare provider about all medications you are taking, including over-the-counter medications, vitamins, and herbal supplements, before starting BESPONSA treatment. Your medical team will evaluate all potential interactions and adjust your treatment plan as necessary.

What Is the Correct Dosage of BESPONSA?

Quick answer: BESPONSA is administered as an intravenous infusion over 1 hour. The recommended total dose in cycle 1 is 1.8 mg/m² per cycle, divided over three doses on days 1, 8, and 15. Subsequent cycle doses depend on whether the patient achieves remission. A doctor or nurse administers the drug in a hospital or clinic — it is never self-administered.

Adults

BESPONSA dosing is calculated based on body surface area (BSA), measured in mg/m². The dosing regimen differs between the first cycle and subsequent cycles, and subsequent cycle dosing depends on whether the patient has achieved a complete remission (CR) or complete remission with incomplete hematologic recovery (CRi).

*Cycle 1 may be extended to 28 days for patients who achieve CR/CRi and/or to allow recovery from toxicity. Day 8 and 15 doses may be adjusted by ±2 days, provided there are always at least 6 days between doses.

Children and Adolescents

BESPONSA is not approved for use in patients under 18 years of age. There is no established pediatric dosing regimen. Clinical trials in the pediatric population are limited, and the safety and efficacy of BESPONSA in children have not been established. Pediatric oncologists may consider BESPONSA on a case-by-case basis as part of compassionate use or clinical trial programs, but this is outside the scope of the approved indication.

Elderly Patients

No dose adjustment is required based on age alone. In the pivotal INO-VATE ALL study, approximately 26% of patients were aged 55 years or older. Elderly patients may be at increased risk of hepatotoxicity, particularly VOD/SOS. Careful monitoring of liver function and close attention to dose modifications based on toxicity are essential in this population.

Premedication

Before each infusion of BESPONSA, patients receive premedication to reduce the risk of infusion-related reactions. This typically includes:

• A corticosteroid (e.g., dexamethasone)
• An antipyretic (fever-reducing medication)
• An antihistamine

Before treatment, patients may also receive medications and intravenous fluids to prevent tumor lysis syndrome, particularly during the first infusion when tumor burden may be high.

Missed Dose

Since BESPONSA is administered by healthcare professionals in a clinical setting, missed doses are uncommon. If a scheduled dose is delayed, your healthcare team will determine the appropriate timing for your next dose. There should always be at least 6 days between individual doses within a cycle. If treatment is interrupted, the dosing schedule will be adjusted accordingly.

Overdose

There is no specific antidote for BESPONSA overdose. In the event of an overdose, the patient should be closely monitored for signs and symptoms of adverse reactions, particularly hepatotoxicity and myelosuppression, and appropriate supportive care should be provided. In clinical trials, the highest single dose tested was 1.8 mg/m². Overdose may lead to more severe or prolonged myelosuppression, liver toxicity, and other adverse effects.

Administration Instructions (For Healthcare Professionals)

BESPONSA is intended for intravenous use only. The infusion must be administered over 1 hour. It must not be given as an intravenous push or bolus injection. The drug must be reconstituted and diluted before administration:

What Are the Side Effects of BESPONSA?

Quick answer: Like all medicines, BESPONSA can cause side effects. The most common include low blood counts, infections, fatigue, nausea, fever, and liver enzyme elevations. Serious side effects include hepatic veno-occlusive disease (VOD/SOS), severe myelosuppression, infusion reactions, tumor lysis syndrome, and QT prolongation. Tell your doctor immediately if you experience rapid weight gain, severe abdominal pain, jaundice, difficulty breathing, or irregular heartbeat.

Clinical trials and post-marketing experience have identified a range of side effects associated with BESPONSA treatment. The severity and frequency of these effects can vary between patients. Your healthcare team will monitor you closely throughout treatment and may adjust your dose or provide supportive medications to manage side effects.

Hepatic Veno-Occlusive Disease (VOD/SOS)

VOD/SOS is the most clinically significant adverse effect associated with BESPONSA. In the pivotal INO-VATE study, VOD/SOS occurred in approximately 14% of patients who received BESPONSA, with a higher incidence (approximately 22%) in patients who subsequently underwent hematopoietic stem cell transplantation. Risk factors for developing VOD/SOS include:

• Receiving more than 2 cycles of BESPONSA before HSCT
• Dual-alkylator or thiotepa-based HSCT conditioning regimens
• Last pre-transplant bilirubin level ≥ upper limit of normal (ULN)
• Older age
• Prior or concurrent hepatotoxic medications
• History of liver disease or prior HSCT

Reporting Side Effects

Reporting suspected side effects after a medicine has been authorized is important. It allows continuous monitoring of the benefit-risk balance. Healthcare professionals and patients are encouraged to report suspected adverse reactions to their national pharmacovigilance authority. In the EU, reports can be submitted through national reporting systems. In the US, reports can be made to the FDA MedWatch program.

How Should You Store BESPONSA?

Quick answer: Unopened BESPONSA vials should be stored refrigerated at 2–8°C (36–46°F) in the original carton to protect from light. Do not freeze. After reconstitution, use immediately or refrigerate for up to 4 hours. The maximum total time from reconstitution to completion of infusion is 8 hours.

Proper storage of BESPONSA is essential to maintain its stability and efficacy. As this is a hospital-administered medication, storage is typically managed by pharmacy staff, but patients and caregivers should be aware of the following requirements:

Before use, the solution should be visually inspected for particulate matter and discoloration. The reconstituted solution should be clear to slightly opalescent, colorless, and free of visible particles. Do not use if particles or discoloration are observed. Unused medicine should not be disposed of via wastewater or household waste. Ask your pharmacist how to dispose of medicines no longer in use — these measures help to protect the environment.

What Does BESPONSA Contain?

Quick answer: Each BESPONSA vial contains 1 mg of the active substance inotuzumab ozogamicin as a white to off-white lyophilized powder. Inactive ingredients (excipients) include sucrose, polysorbate 80, sodium chloride, and tromethamine. After reconstitution with 4 mL of water for injection, each mL contains 0.25 mg of inotuzumab ozogamicin.

Appearance and Packaging

BESPONSA is supplied as a powder for concentrate for solution for infusion. Each package contains one glass vial holding a white to off-white lyophilized cake or powder. The product is manufactured by Pfizer Service Company BV (Zaventem, Belgium) and marketed by Pfizer Europe MA EEIG (Brussels, Belgium).

The reconstituted solution should appear clear to slightly opalescent, colorless, and free from visible foreign particles. The density of the reconstituted solution is approximately 1.02 g/mL at 20°C. Inotuzumab ozogamicin is light-sensitive and must be protected from ultraviolet light during reconstitution, dilution, and administration.