# Clinical Case Report on the Use of Rezafungin in Pneumocystis jirovecii Pneumonia in a Critically Ill Patient

## TL;DR

A patient with severe Pneumocystis pneumonia received rezafungin when standard treatment was not possible, showing some promise but also highlighting the need for further research.

## Contribution

This is the first reported case of rezafungin use in Pneumocystis jirovecii pneumonia in a critically ill human patient.

## Key findings

- Rezafungin was used in a patient with PJP when standard therapy was contraindicated.
- The patient showed a partial biomarker response but ultimately developed multiorgan failure.
- The case suggests rezafungin may be a potential treatment option for PJP in specific clinical scenarios.

## Abstract

Pneumocystis jirovecii pneumonia (PJP) is a life-threatening opportunistic infection predominantly affecting immunocompromised patients. Trimethoprim–sulfamethoxazole (TMP–SMX) remains the standard therapy but is often limited by severe toxicity. Rezafungin, a next-generation echinocandin with a long half-life, has shown preclinical activity against Pneumocystis spp., but its use in humans remains largely unexplored. We report the case of a 67-year-old man with inflammatory bowel disease who developed severe PJP complicated by acute respiratory failure, septic shock, and multiorgan dysfunction following corticosteroid and biologic therapy. Standard TMP–SMX therapy was contraindicated due to renal impairment and pancytopenia. The patient received rezafungin via a compassionate-use programme, with serial monitoring of serum and bronchoalveolar β-D-glucan levels. Despite a partial biomarker response, the patient ultimately progressed to refractory acute respiratory distress syndrome and multiorgan failure. This case provides preliminary human data suggesting that rezafungin may offer a potential therapeutic option for PJP when standard treatment is contraindicated or poorly tolerated. Close clinical and biomarker monitoring is essential. Further clinical and experimental studies are warranted to determine its efficacy, optimal dosing, and safety in critically ill immunocompromised patients.