Background and Importance Teclistamab is a bispecific antibody (BsAb) targeting the CD3 receptor complex on T cells and BCMA on B cells. This treatment is the process of approval for patients with relapsed or refractory multiple myeloma (RRMM). It is only available in some countries through an Expanded-Access Program. The posology consists of two set up-doses of 60 and 300 µg/Kg separated 2–4 days, and treatment doses of 1500 µg/Kg administered weekly. Hospitalisation is required for at least 48 hours from the start of administration of the two set-up doses and the first treatment dose.

It has been observed that the administration of BsAb such as Teclistamab might cause the cytokine release syndrome (CRS). CRS is a potentially life-threatening, systemic inflammatory response.

Given the BsAb market is growing rapidly, it is important to train the healthcare professionals to good handling these adverse reactions.

Aim and Objectives To describe the CRS produced by Teclistamab in one patient with RRMM and the management of this adverse reaction.

Material and Methods A case report identified in a tertiary hospital in 2022. Clinical data were collected through the electronic medical record.

Results A 76-year-old man with hypertension history and diagnosed with RRMM, was admitted to hospital to be treated with Teclistamab. Just 24 hours after the first set-up dose, the patient experienced CRS-related symptoms such as chills and a hypertensive crisis (300/140 mmHg). He was treated with a dose of Tocilizumab 600 mg, corticosteroids, antipyretics and oral antihypertensives, without clinical improvement. The patient was transferred to the Intensive Care Unit (ICU) for the management of his hypertension. At the ICU, he received two more doses of Tocilizumab 600 mg every 8 hours. The hypertension was controlled with oral antihypertensive drugs and the patient was discharged from the ICU the following day.

The subsequent doses of Teclistamab were well tolerated and the patient did not experience any other adverse reaction.

Conclusion and Relevance Although CRS is predictable in patients who receive BsAb and it is well controlled with Tocilizumab, it is important to monitor the patients within the 24–48 hours after the first administration of Teclistamab. This monitoring is particularly crucial for those patients with history of arterial pressure alterations.

Conflict of Interest No conflict of interest