About This Guide

This guide explains the functionality and clinical context for the Kimmtrak (tebentafusp) Dosing Calculator. It details the tool's inputs, outputs, and the dosing principles it is based on, such as the mandatory step-up schedule and missed dose rules. This information is intended to supplement, not replace, the full prescribing information and professional clinical judgment.

Outputs

After processing the inputs, the calculator provides a clear, actionable summary for the planned infusion date, including:

• Recommended Dose: The specific dose in micrograms (mcg) to be administered (e.g., 20 mcg, 30 mcg, or 68 mcg).
• Volume to Withdraw: The precise volume in milliliters (mL) to be drawn from a standard 100 mcg/0.5 mL (200 mcg/mL) vial.
• Dose Justification: The clinical reason for the recommended dose (e.g., "Dose 2 of step-up schedule" or "Restarting step-up schedule due to missed dose").
• Projected Dosing Schedule: A forward-looking table showing the planned dates and dosages for the next several weekly infusions, helping with patient scheduling.

How to Use

The calculator operates in two modes based on the patient's treatment history.

New Patient (Starting Kimmtrak)

For patients who have not yet received any dose of Kimmtrak, select the "New Patient" option. You only need to input the Date of First Dose. The tool will automatically calculate the complete step-up dosing schedule starting with the initial 20 mcg dose on the selected date.

Existing Patient (On Kimmtrak)

For patients already undergoing treatment, select "Existing Patient" and provide three pieces of information:

1. Last Dose Administered: Select the most recent dose the patient received from the dropdown menu (e.g., Dose 1, Dose 2, Maintenance Dose).
2. Date of Last Dose: Enter the exact date the last infusion was given.
3. Date of Planned Next Dose: Enter the upcoming date for the next scheduled infusion.

The tool uses these dates to determine if the treatment is on schedule or if a missed dose has occurred, adjusting the next dose accordingly.

Dosing Overview

Kimmtrak requires a mandatory weekly step-up dosing schedule for the first three doses to mitigate the risk of Cytokine Release Syndrome (CRS). The calculator follows this schedule precisely.

Switching

This calculator is not designed to provide guidance on switching to Kimmtrak from other systemic therapies. The initiation of Kimmtrak should always follow the standard new patient step-up dosing schedule as outlined in the prescribing information, regardless of prior treatments. Clinical decisions regarding treatment transitions should be made by the treating physician.

Missed Dose

The calculator incorporates the critical missed dose rule from the prescribing information. The time between each weekly dose of Kimmtrak should not exceed 7 days.

Safety Alerts

The calculator's output includes a reminder of the boxed warning for Kimmtrak regarding Cytokine Release Syndrome (CRS).

Healthcare providers should consult the full prescribing information for detailed guidance on pre-medication, monitoring, and management of CRS and other potential adverse reactions.

FAQ

What happens if a patient misses a dose by exactly 8 days?

If the interval is more than 7 days, the calculator will flag this as a missed dose and recommend restarting the step-up schedule at 20 mcg.

Does this tool account for dose reductions due to adverse events?

No. The calculator only follows the standard dosing and missed dose protocols. Dose modifications or interruptions due to toxicity must be managed according to the guidelines in the official prescribing information and require independent clinical judgment.

What vial concentration does the calculator use for its volume calculation?

The tool calculates the volume to withdraw based on the standard Kimmtrak single-dose vial concentration of 100 mcg/0.5 mL, which is equivalent to 200 mcg/mL.

Can I use this tool for a patient who is not being dosed weekly?

No. The tool is programmed for the approved weekly dosing schedule. Any deviation from this schedule that results in an interval greater than 7 days will trigger the "missed dose" protocol.

Why does the tool require a "Planned Next Dose" date for existing patients?

This date is essential for calculating the interval since the last dose, which determines whether the patient can proceed to the next scheduled dose or must restart the step-up protocol.

Is the projected schedule binding?

No, the projected schedule is for planning and informational purposes only. Actual administration dates may vary, and if a future dose is delayed by more than 7 days, the step-up protocol must be restarted.

What if the patient's last dose was the third dose (68 mcg)?

You should select "Dose 3 (68 mcg)" from the "Last Dose Administered" dropdown. The calculator will then recommend the first maintenance dose (also 68 mcg) for the next infusion, provided it is within 7 days.

Does the calculator provide information on drug preparation or administration?

The tool only provides the final dose and volume. It does not provide detailed instructions on dilution, preparation of the infusion bag, or administration technique. Always refer to the official prescribing information for these procedures.

References

• KIMMTRAK (tebentafusp-tebn) US Prescribing Information - U.S. Food and Drug Administration (FDA)
• Kimmtrak (tebentafusp) European Public Assessment Report (EPAR) - European Medicines Agency (EMA)
• Kimmtrak Official Healthcare Professional Website - Immunocore
• Tebentafusp Professional Drug Information - Drugs.com