P-680 Comparison of ovarian hyperstimulation syndrome (OHSS) rates resulting from conventional dosing versus personalized dosing of follitropin delta in ovarian stimulation, analysis of RITA, ESTHER-1 trials
Authors: Grover S , Foster E  D , Heiser P  W 
Published: July 2024

Abstract

Study question
To compare OHSS rates with conventional dosage of follitropin delta in the RITA-1 and RITA-2 trials (hereafter ‘RITA’) to personalized dosing in the ESTHER-1 trial.

Summary answer
RITA and ESTHER-1 had similar efficacy and OHSS rates despite differences in dosing regimens, possibly due to differences in fresh transfer cancellation rates.

What is known already
Follitropin delta is a human cell-line derived follicle stimulating hormone whose fixed dosage in ovarian stimulation, personalized based upon body weight and serum anti-Müllerian hormone (AMH) and body weight, has been shown to be safe and effective in Gonadotrophin Releasing Hormone (GnRH) antagonist ovarian stimulation protocols. In the present trial, conventional dosing of follitropin delta allowing for dose revisions has been evaluated in GnRH antagonist ovarian stimulation protocols to demonstrate the broad utility of this gonadotrophin therapeutic and to address United States (US) regulatory considerations.

Study design, size, duration
RITA were randomized, double-blind, controlled, US multicentre trials of follitropin delta. The primary endpoint was cumulative ongoing pregnancy rate after fresh/frozen transfers within 12 months of cycle start. 1058 women 18-42 years randomized 10:1 to follitropin delta or placebo.
ESTHER-1 was a randomized, European multicentre, assessor-blind, noninferiority trial of follitropin delta. The primary endpoints were fresh transfer ongoing pregnancy and implantation rates. 1329 women 18-40 years randomized 1:1 to follitropin delta or follitropin alfa.

Participants/materials, setting, methods
In RITA, 12 µg/day, 15 µg/day dosages were used for 4 days: 18-34 or 35-42 years, respectively, with 3 µg dose adjustments thereafter depending on response. Human chorionic gonadotropin (hCG) was used if &lt; 20 follicles of ≥ 12 mm and estradiol level &lt;3,000 pg/mL. Else, agonist trigger and fresh transfer cancellation; ≥20 oocytes retrieved also cancelled fresh transfer.
In ESTHER-1, hCG was used if &lt; 25 follicles of ≥ 12 mm. Else, agonist trigger, and fresh transfer cancellation.

Main results and the role of chance
The ongoing pregnancy rate per fresh transfer with follitropin delta was 41.9% in RITA and 36.3% in ESTHER-1. The primary efficacy endpoint was met for all 3 trials. Rates and severity defined by Golan criteria of OHSS observed in RITA and ESTHER-1 were similar, respectively for: all OHSS, any grade (3.1% versus 3.5%), Grade 1 (0.3% versus 0.5%), Grade 2 (0.8% versus 0.9%), Grade 3 (1.8% versus 1.1%), Grade 4 (0.2% versus 0.6%), and Grade 5 (0.1% versus 0.5%). The rate of early OHSS, defined as onset ≤9 days after trigger of final follicular maturation, was also similar, respectively for any grade (2.2% versus 2.6%), Grade 1 (0.3% versus 0.3%), Grade 2 (0.6% versus 0.9%), Grade 3 (1.1% versus 0.8%), Grade 4 (0.1% versus 0.3%) and Grade 5 (0.1 % versus 0.3%). However, the fresh transfer cancellation rate was &gt;3x higher in RITA (35.2%) than in ESTHER-1 (11.1%).

Limitations, reasons for caution
Other reasons for transfer cancellation in all trials included adverse events or no blastocyst available for transfer; however, no significant differences were observed. A placebo comparator was selected for RITA to meet regulatory requirements for double-blinding; women with ≤3 oocytes retrieved were offered support for treatment outside of the trials.

Wider implications of the findings
Stimulation with follitropin delta is effective and associated with low rates of OHSS when used with either conventional or personalized dosing. However, stricter criteria for the use of hCG as trigger and allowance of fresh transfer may be required with conventional dosing to maintain this safety profile.

Trial registration number
NCT01956110, NCT03740737, NCT03738618