The Monjuvi (tafasitamab) dosing calculator is a support tool for healthcare professionals to determine patient-specific dosing based on the approved prescribing information. This guide provides supplementary context on the calculator's outputs, usage, and the underlying clinical data for Monjuvi when used in combination with lenalidomide for relapsed or refractory diffuse large B-cell lymphoma (DLBCL).

After entering the required patient data, the calculator provides a comprehensive summary for preparation and administration. Key outputs include:

• Calculated Total Dose (mg): The patient-specific dose of tafasitamab, calculated at 12 mg/kg based on the actual body weight entered.
• Number of Vials (200 mg): The minimum number of 200 mg single-dose vials required to prepare the calculated dose.
• Total Volume to Withdraw (mL): The total volume of reconstituted solution (40 mg/mL) to be withdrawn from the vials for dilution.
• Preparation & Administration Guidelines: Step-by-step instructions for reconstitution, dilution in a 250 mL bag of 0.9% Sodium Chloride, and cycle-specific infusion rate recommendations.

To ensure accurate calculations, follow these steps:

1. Enter Patient Weight: Input the patient's actual body weight. Select the appropriate unit (kg or lbs). The tool will automatically convert lbs to kg for the dose calculation.
2. Select Treatment Cycle: Choose the current treatment cycle from the dropdown menu (Cycle 1, Cycle 2, or Cycle 3 and beyond).
3. Select Treatment Day: Once a cycle is selected, choose the corresponding administration day (e.g., Day 1, 4, 8, 15, or 22 for Cycle 1).
4. Calculate: Click the "Calculate Dose" button to generate the results. The outputs are based on the standard 12 mg/kg dosing regimen.

The recommended dosage of Monjuvi is 12 mg/kg based on actual body weight, administered as an intravenous infusion. It is given in combination with lenalidomide for up to 12 cycles, and then as Monjuvi monotherapy until disease progression or unacceptable toxicity. Each cycle is 28 days.

Premedication should be administered 30 to 60 minutes prior to starting the infusion to reduce the risk of infusion-related reactions (IRRs).

Dose adjustments for Monjuvi are managed by modifying the infusion rate or withholding doses, not by reducing the dose itself. Management of severe adverse reactions may require treatment interruption.

Infusion-Related Reactions (IRRs):

• Grade 2 (Moderate): Interrupt the infusion. Once symptoms resolve, resume at 50% of the previous rate.
• Grade 3 (Severe): Interrupt the infusion. Once symptoms resolve, resume at 25% of the previous rate.
• Grade 4 (Life-threatening): Discontinue Monjuvi treatment permanently.

Hematologic Toxicities:

• For Grade 3 or 4 neutropenia or thrombocytopenia, withhold Monjuvi and lenalidomide. Refer to the full prescribing information for specific criteria for resuming treatment.

If a planned dose of Monjuvi is missed, it should be administered as soon as possible. The schedule of subsequent administrations should be adjusted accordingly to maintain the specified treatment interval.

Healthcare professionals should be aware of the key safety information associated with Monjuvi:

• Infusion-Related Reactions (IRRs): Monjuvi can cause IRRs, including anaphylaxis. Patients should be monitored closely during the infusion. Premedication is recommended to reduce the risk.
• Myelosuppression: Monjuvi can cause serious or severe myelosuppression, including neutropenia, thrombocytopenia, and anemia. Complete blood counts should be monitored throughout treatment.
• Infections: Serious and fatal infections, including opportunistic infections, have been observed. Patients should be monitored for signs and symptoms of infection.
• Embryo-Fetal Toxicity: Based on its mechanism of action, Monjuvi can cause fetal B-cell depletion when administered to a pregnant woman. Verify pregnancy status in females of reproductive potential prior to starting treatment.

What is the concentration of Monjuvi after reconstitution?
After reconstituting a 200 mg vial with 5 mL of Sterile Water for Injection (SWFI), the final concentration is 40 mg/mL.

What is the recommended infusion rate for the first dose?
For Cycle 1, Day 1, the infusion should be started at 70 mL/hr for the first 30 minutes. If well-tolerated, the rate can be increased to 140 mL/hr for the remainder of the infusion.

What is the total infusion time for doses after Cycle 1, Day 1?
Subsequent infusions after the very first dose should be administered over 1.5 to 2 hours.

Can the infusion bag be shaken after dilution?
No. To avoid foaming and denaturation of the protein, the infusion bag should be mixed gently by inverting it. Do not shake the vial or the bag.

Is premedication required for every dose?
Yes, premedication with an antihistamine, antipyretic, and H2-receptor antagonist is recommended before each infusion. A glucocorticoid is required for Cycle 1, Day 1 and may be considered for subsequent infusions based on clinical judgment.

How many vials are needed for an 85 kg patient?
The total dose would be 85 kg * 12 mg/kg = 1020 mg. Since each vial contains 200 mg, you would need ceil(1020 / 200) = 6 vials.

What should be done if a patient's weight changes significantly during treatment?
The dose of Monjuvi is based on the patient's actual body weight. It is standard practice to re-evaluate the dose if there is a clinically significant change in weight.

How is Monjuvi stored after reconstitution and dilution?
If not used immediately, the reconstituted solution in the vial can be stored for up to 24 hours refrigerated. The diluted solution in the infusion bag can also be stored for up to 24 hours refrigerated, followed by up to 12 hours at room temperature (including infusion time).

1. MONJUVI® (tafasitamab-cxix) for injection, for intravenous use. U.S. Prescribing Information. Incyte Corporation.
2. Monjuvi (tafasitamab-cxix) HCP Website. Incyte Corporation.
3. Minjuvi (tafasitamab) European public assessment report (EPAR). European Medicines Agency.
4. Salles G, Duell J, González Barca E, et al. Tafasitamab plus lenalidomide in relapsed or refractory diffuse large B-cell lymphoma (L-MIND): a multicentre, prospective, single-arm, phase 2 study. Lancet Oncol. 2020;21(7):978-988. doi:10.1016/S1470-2045(20)30225-4