Letrozole SIE is an investigational medicine to treat hormone receptor-positive breast cancer and is expected to provide sustained and stable oestrogen suppression.
Laboratorios Farmacéuticos ROVI S.A. (hereinafter, “ROVI”) has announced that, on 31 March, it received authorisation from the Spanish Agency of Medicines and Medical Devices to conduct a new clinical trial with Letrozole SIE in Spain. With this trial, it aims to evaluate the comparative bioavailability after multiple doses of Letrozole SIE and the reference medicine (Femara®) in postmenopausal women with early breast cancer who have previously received endocrine therapy.
This clinical trial forms part of ROVI’s LAISOLID project, funded by the CDTI within the framework of the Spanish Recovery, Transformation and Resilience Plan under the Med4Cure IPCEI programme.
Letrozole SIE (“Superior Inhibition of Estrogens”) is an investigational medicine that ROVI is developing to treat postmenopausal women with hormone receptor-positive breast cancer. It is a long-acting injectable (LAI) formulation of letrozole designed to provide sustained and stable oestrogen suppression during months, which could potentially have a positive impact on the disease’s progression.
The preliminary results of a Phase 1 single-dose study (LEILA-1)* recently completed in Europe support progression to the next stages of the clinical development programme.
As previously reported by the company, the clinical programme for Letrozole SIE includes two additional clinical trials apart from LEILA-1: a bioavailability study versus oral letrozole (SIE-1) and a Phase III clinical trial to demonstrate the efficacy and safety of this new medicine (SIE-3).
In July 2025, ROVI contacted the U.S. Food and Drug Administration (FDA) to agree on the clinical pathway of the product and, in November 2025, the agency approved the SIE-1 bioavailability clinical trial to be conducted in the United States. Likewise, as mentioned previously, ROVI has received approval to begin the same study in Spain. Therefore, the company plans to commence recruitment of the women who will participate in this study in both countries within the next few months.
*Evaluation of the Pharmacokinetics, Safety, and Tolerability of IM Letrozole LEBE in Healthy Post-menopausal Women (LEILA-1). National Library of Medicine. ClinicalTrials.gov. NCT06315205 (available at: https://clinicaltrials.gov/study/NCT06315205)
