Linzagolix in Adenomyosis and Recurrent Implantation Failure (LINZA-RIF)

Efficacy of Linzagolix 200 mg for 3 to 6 Months Prior to Embryo Transfer in Patients With Adenomyosis and Recurrent Implantation Failure: A Prospective Case Series

Adenomyosis is associated with impaired endometrial receptivity and reduced implantation rates in assisted reproduction, even when using high-quality embryos. Linzagolix (Yselty, 200 mg) is an oral GnRH receptor antagonist approved for uterine fibroids with a favourable tolerability profile and rapid elimination half-life (18-20 hours) compared to GnRH agonists.

This prospective case series evaluates the efficacy of linzagolix 200 mg administered for 3 to 6 months prior to embryo transfer in patients with confirmed adenomyosis and recurrent implantation failure (RIF), defined as ≥2 failed transfers with high-quality blastocysts (≥BB Gardner in oocyte donation, or PGT-A confirmed euploid in autologous cycles).

The primary endpoint is the live birth rate (LBR) per embryo transfer. Secondary endpoints include clinical pregnancy rate, miscarriage rate, morphological response of adenomyosis (uterine volume and junctional zone [JZ] thickness assessed by standardised transvaginal ultrasound), and tolerability profile. The study also explores the optimal treatment duration (3 vs 6 months) as a sub-analysis based on morphological response at the month-3 visit.

The study is conducted at three centres of Vida Fertility Institute (Madrid, Alicante and San Sebastián, Spain). Sample size: n=35 patients. Study duration: 24 months.

Study Overview

• Status: Not yet recruiting
• Conditions: Embryo Transfer; Adenomyosis of Uterus; Implantation Failure; Infertility Female
• Intervention / Treatment: Drug: Linzagolix 200 mg (Yselty)

Detailed Description

BACKGROUND:

Current standard of care for adenomyosis prior to embryo transfer in RIF patients consists of GnRH agonist therapy (triptorelin depot) for 1-3 months, with or without letrozole. This approach requires intramuscular administration, is associated with intense vasomotor symptoms, and has a prolonged pharmacological residual effect (4-6 weeks) that complicates cycle planning. No prospective study has evaluated linzagolix in this specific clinical scenario.

DESIGN:

Prospective before-after case series. Each patient serves as her own historical control (prior failed transfers under standard care vs outcome after linzagolix treatment). Treatment duration (3 or 6 months) is determined by morphological response at the month-3 ultrasound visit. Endometrial preparation is initiated 7 days after the last dose of linzagolix.

ULTRASOUND PROTOCOL:

Standardised transvaginal ultrasound measurements at each visit: uterine volume (L x AP x T x 0.523 cm3), junctional zone maximum (mm), junctional zone minimum (mm) and junctional zone difference (mm). All measurements performed in strict sagittal plane with ≥7 MHz transvaginal probe.

VASOMOTOR SYMPTOM MANAGEMENT:

Standardised non-estrogenic supplementation protocol (Cimicifuga racemosa 20 mg, Remifemin) if EVA score ≥4 for hot flushes or insomnia. Suspended simultaneously with the last dose of linzagolix.

REGULATORY FRAMEWORK:

Observational study with medicinal products (EOMF) under Spanish Royal Decree 957/2020. Use of linzagolix in this indication is off-label. Study approved by CEIm del Hospital Clinico San Carlos, Madrid.

• Study Type: Observational
• Enrollment (Estimated): 35

Contacts and Locations

• Study Contact: Name: Elena De Santiago Romero, MD; Phone Number: +34 679211353; Email: santiago.e@vidafertility.com
• Study Contact Backup: Name: Irene Hervas, PhD; Phone Number: +34 697766609; Email: hervas.i@vidafertility.com

Study Locations

• Spain
  • Alicante
    • Alicante, Alicante, Spain, 03008
      • Vida Fertility Alicante
      • Contact: Sergio Rogel, MD; Phone Number: +34 669657631; Email: rogel.s@vidafertility.com
      • Contact: Alejandra García Villalba, MD; Phone Number: +34 605920083; Email: garciavillalba.a@vidafertility.com
  • Gipuzkoa
    • San Sebastián, Gipuzkoa, Spain, 20018
      • Vida Fertility Donostia
      • Contact: Estefanía Rodriguez, MD; Phone Number: +34 653733284; Email: rodriguez.e@vidafertility.com
  • Madrid
    • Madrid, Madrid, Spain, 28043
      • Vida Fertility Institute Madrid
      • Contact: Elena De Santiago Romero, MD; Phone Number: +34 679211353; Email: santiago.e@vidafertility.com
      • Contact: Irene Hervas, PhD; Phone Number: +34 697766609; Email: hervas.i@vidafertility.com

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: No

• Sampling Method: Non-Probability Sample

Study Population

Women aged 18 to 50 years with confirmed adenomyosis (transvaginal ultrasound or MRI) and recurrent implantation failure, defined as 2 or more failed embryo transfers with high-quality blastocysts (grade BB or above in oocyte donation cycles, or PGT-A confirmed euploid blastocysts in autologous cycles), attending Vida Fertility Institute centres in Madrid, Alicante and San Sebastian, Spain.

Description

Inclusion Criteria:

• Age 18 to 50 years
• Confirmed adenomyosis by transvaginal ultrasound or MRI
• Recurrent implantation failure defined as 2 or more failed embryo transfers with high-quality blastocysts: oocyte donation recipients (blastocyst grade BB or above, Gardner classification) OR autologous IVF cycles with PGT-A confirmed euploid blastocysts
• Normal uterine cavity with no submucosal distortion
• At least 1 suitable embryo available for transfer (blastocyst grade BB or above, or PGT-A euploid)
• Signed written informed consent including explicit acknowledgement of off-label use of linzagolix

Exclusion Criteria:

• Untreated hydrosalpinx
• Untreated stage III-IV endometriosis
• Major uterine anomaly (uterine septum, bicornuate uterus)
• Known contraindication to linzagolix including known hepatopathy
• Prior treatment with linzagolix
• GnRH analogue treatment within 6 months prior to enrolment
• BMI greater than 35 kg/m2
• Prior failed transfers exclusively with embryos below the quality threshold (below BB grade, non-euploid)

Study Plan

How is the study designed?

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort

Intervention / Treatment

Linzagolix 200 mg - Adenomyosis and RIF; Patients with confirmed adenomyosis and recurrent implantation failure (2 or more failed embryo transfers with high-quality blastocysts: grade BB or above in oocyte donation cycles, or PGT-A confirmed euploid in autologous cycles) receiving linzagolix 200 mg orally once daily for 3 to 6 months prior to embryo transfer. Treatment duration is determined by morphological response assessed at the month-3 transvaginal ultrasound visit. Endometrial preparation is initiated 7 days after the last dose of linzagolix.

Drug: Linzagolix 200 mg (Yselty); Linzagolix 200 mg orally once daily for a minimum of 3 months, extendable to 6 months based on morphological response (uterine volume and junctional zone assessment) at the month-3 transvaginal ultrasound visit. Off-label use for adenomyosis prior to embryo transfer.; Other Names: Yselty; GnRH receptor antagonist

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Live Birth Rate (LBR) per embryo transfer	Proportion of embryo transfers resulting in the birth of a live neonate at or beyond 24 weeks of gestation.	Up to 12 months after embryo transfer

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Clinical Pregnancy Rate	Proportion of embryo transfers resulting in the presence of an intrauterine gestational sac with fetal heartbeat on transvaginal ultrasound at 6-7 weeks of gestation.	6-7 weeks after embryo transfer
Miscarriage Rate	Proportion of clinical pregnancies ending in spontaneous pregnancy loss before 22 weeks of gestation.	Up to 22 weeks of gestation
Change in Uterine Volume	Change in uterine volume (cm3) measured by transvaginal ultrasound using the ellipsoid formula (L x AP x T x 0.523) from baseline to post-treatment.	Baseline, month 3, month 6 (if applicable) and pre-transfer (approximately 3-7 months from baseline)
Change in Junctional Zone Maximum Thickness	Change in junctional zone (JZ) maximum thickness (mm) measured by standardised transvaginal ultrasound in strict sagittal plane from baseline to post-treatment.	Baseline, month 3, month 6 (if applicable) and pre-transfer (approximately 3-7 months from baseline)
Incidence of Vasomotor Adverse Events	Proportion of patients reporting hot flushes, insomnia or other vasomotor symptoms, assessed using a visual analogue scale (EVA 0-10) at each visit.	Monthly during treatment period (up to 6 months)

Collaborators and Investigators

• Sponsor: Vida Fertility Institute

Study record dates

Study Major Dates

• Study Start (Estimated): September 1, 2026
• Primary Completion (Estimated): July 1, 2028
• Study Completion (Estimated): September 1, 2028

Study Registration Dates

• First Submitted: July 6, 2026
• First Submitted That Met QC Criteria: July 6, 2026
• First Posted (Actual): July 13, 2026

Study Record Updates

• Last Update Posted (Actual): July 13, 2026
• Last Update Submitted That Met QC Criteria: July 6, 2026
• Last Verified: July 1, 2026

More Information

Terms related to this study

• Keywords: oocyte donation; PGT-A; endometrial receptivity; GnRH antagonist; live birth rate; Linzagolix; recurrent implantation failure; adenomyosis; junctional zone; Yselty
• Additional Relevant MeSH Terms: Urogenital Diseases; Genital Diseases; Female Urogenital Diseases; Female Urogenital Diseases and Pregnancy Complications; Uterine Diseases; Genital Diseases, Female; Infertility; Adenomyosis; Infertility, Female; linzagolix
• Other Study ID Numbers: VFI-LNZG-2025

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED
• IPD Plan Description: Individual participant data will not be shared at this stage due to the small sample size and the need to protect patient privacy in accordance with the General Data Protection Regulation (GDPR, EU 2016/679) and Spanish Organic Law 3/2018 on Personal Data Protection. Anonymised aggregate data may be made available upon reasonable request following publication of the primary results.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No