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Randomized Controlled Trial of Combined Letrozole and Clomid (CLC II) Versus Letrozole Alone for Women With Anovulation

Randomized Controlled Trial of Combined Letrozole and Clomid (CLC II) Versus Letrozole Alone for Women With Anovulation

Status
Active, not recruiting
Phases
Phase 4
Study type
Interventional
Source
ClinicalTrials.gov
Registry ID
NCT05206448
Acronym
CLC II
Enrollment
190
Registered
2022-01-25
Start date
2020-10-26
Completion date
2025-12-31
Last updated
2025-04-15

For informational purposes only — not medical advice. Sourced from public registries and may not reflect the latest updates. Terms

Conditions

Infertility, PCOS, Polycystic Ovary Syndrome

Brief summary

This study evaluates the addition of clomiphene citrate (CC) to letrozole for the treatment of infertility in women with polycystic ovary syndrome across a course of two treatment cycles with stair step dosing of letrozole similar to standard of care. Half of the participants will receive letrozole and CC in combination, while the other half will receive letrozole alone.

Detailed description

Letrozole and Clomid are both used for ovulation induction, but they have different mechanisms of action. In a pilot study we found that the combination of letrozole 2.5 mg and CC 50 mg nearly doubled the ovulation rate as compared to use of letrozole monotherapy (77% vs. 43%, P=0.007; rate ratio for ovulation (95% CI) 1.80 (1.18 to 2.75), with similar endometrial thickness and number of follicles across treatment arms among those who ovulated. Additional data is needed to evaluate escalating dosages, multiple cycles, live birth and multiple gestation with this novel treatment combination. This is a randomized controlled trial of letrozole versus letrozole and clomiphene citrate (CC) for up to three menstrual cycles. Women will be randomized in a 1:1 ratio to receive letrozole 2.5 mg or combination of letrozole 2.5 mg and clomiphene 50 mg for 5 days on days 3-7 of menstrual cycle. The women and their partners will be instructed to have regular intercourse with the intent to conceive during the cycle. Patients will have an transvaginal ultrasound in the mid-luteal phase of cycle to assess corpora lutea number and endometrial thickness. Patients will have mid- luteal phase progesterone level drawn to evaluate ovulation. Patients in both study arms who do not ovulate will have their Letrozole dose increased by 2.5 mg in the next study cycle to a max of 7.5 mg. Patients in the combination arm who do not ovulate will only have their Letrozole dose increased and will continue to receive the same dose of clomiphene across the three study treatment cycles. Side effect profile will also be monitored.

Interventions

DRUGLetrozole

Letrozole tablet

DRUGClomiphene Citrate

Clomiphene Citrate tablet

Sponsors

Society for Reproductive Investigation
CollaboratorUNKNOWN
American Society for Reproductive Medicine
CollaboratorUNKNOWN
University of Wisconsin, Madison
CollaboratorOTHER
Rachel Mejia
Lead SponsorOTHER

Study design

Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
TREATMENT
Masking
NONE

Eligibility

Sex/Gender
FEMALE
Age
18 Years to 40 Years
Healthy volunteers
No

Inclusion criteria

1. Willing to comply with all study procedures and be available for the duration of the study 2. Diagnosis of infertility: Inability of couple to achieve successful pregnancy after 12 months of regular time unprotected intercourse in women less than 35 years of age; and after 6 months of regular intercourse without use of contraception in women 35 years and older. Women that have anovulation or oligomenorrhea are also considered to meet diagnosis of infertility, without meeting the time constraints described above. 3. Diagnosis of polycystic ovary syndrome based on Revised Rotterdam criteria. 4. Ability to have regular intercourse during the ovulation induction phase of the study. 5. Partner with a normal sperm concentration of 15 million/mL and with normal motility of \>40% according to World Health Organization cutoff points or greater than 10 million total motile sperm count OR has fathered a pregnancy in the past.

Exclusion criteria

1. Current pregnancy 2. Current use of hormonal contraception; use of any type of combined contraceptive or oral progestins within the past month; or use of hormonal implants or depo progestins within the past 3 months 3. Other known cause of infertility: endometriosis, tubal factor, uterine abnormalities 4. Uncorrected thyroid disease 5. Untreated hyperprolactinemia 6. Medical conditions in which avoiding pregnancy is recommended until under improved control: poorly controlled Type 1 or Type 2 diabetes, poorly controlled hypertension 7. Contraindications to clomiphene citrate: hypersensitivity to clomiphene citrate or any of its components, history of liver disease or known liver disease, unknown cause of abnormal uterine bleeding, or intracranial lesion 8. Contraindications to letrozole: hypersensitivity to letrozole or any of its components 9. Use of medications known to affect reproductive function or metabolism or that are an absolute contraindication during pregnancy within the past month 10. If patients are suspected based on clinical findings for other etiologies that mimic PCOS, work up must be completed to exclude other etiologies prior to enrollment (i.e. Cushing's syndrome, androgen-secreting tumor)

Design outcomes

Primary

MeasureTime frameDescription
OvulationTested 6 to 8 days following patient reporting a positive ovulation test (LH surge). If no surge is detected, progesterone lab will be drawn on Cycle day 21-24.Number of Participants with Mid-luteal serum progesterone level \>=3 ng/ml Number of cycles with Mid-luteal serum progesterone level \>=3 ng/ml

Secondary

MeasureTime frameDescription
Endometrial ThicknessCycle day 21-24 of 1st treatment cycleEndometrial thickness assessed by ultrasound
Conception5 weeks after treatment in treatment cycles 1, 2, and 3 (treatment cycle is 24-35 days depending on ovulation)positive serum or urinary test of hCG
Clinical Pregnancy6 to 7 weeks after treatment in treatment cycles 1, 2, and 3 (treatment cycle is 24-35 days depending on ovulation)intrauterine pregnancy with fetal heart motion determined by ultrasound
Number of Corpora LuteaCycle day 21-24 of 1st treatment cycleNumber of corpora lutea on ultrasound
Live Birth9-10 months following final treatment cycle (treatment cycle is 24-35 days depending on ovulation)delivery of a live born infant determined by medical record abstraction
Multiple Birth9-10 months following final treatment cycle (treatment cycle is 24-35 days depending on ovulation)delivery of more than one infant determined by medical record abstraction
Pregnancy LossThrough study completion, an average of 1 yearbiochemical pregnancy, miscarriage, or ectopic pregnancy determined by ultrasound or medical record abstraction
Multiple Gestation6 to 7 weeks after treatment in treatment cycles 1, 2, and 3 (treatment cycle is 24-35 days depending on ovulation)intrauterine pregnancy with more than one fetal heart motion determined by ultrasound

Countries

United States

Participant flow

Participants by arm

ArmCount
Letrozole
Letrozole 2.5 mg orally for 5 days on cycle days 3-7 in first study treatment cycle. Participants who ovulate and do not become pregnant will repeat the same treatment protocol for their next study cycle. Participants who do not ovulate will repeat the protocol with Letrozole dose increase of 2.5 mg daily in the next treatment cycle, to a maximum dose of 7.5 mg in the 3rd cycle. Letrozole: Letrozole tablet
98
Letrozole + Clomiphene Citrate
Letrozole 2.5 mg orally for 5 days on cycle days 3-7 AND Clomiphene Citrate 50 mg orally for 5 days on cycle days 3-7. Participants who ovulate and do not become pregnant will repeat the same treatment protocol for their next study cycle. Participants who do not ovulate will repeat the protocol with Letrozole dose increase of 2.5mg daily in the next treatment cycle to a maximum dose of 7.5 mg in the 3rd cycle, while maintaining the same dose of Clomiphene Citrate. Letrozole: Letrozole tablet Clomiphene Citrate: Clomiphene Citrate tablet
92
Total190

Withdrawals & dropouts

PeriodReasonFG000FG001
Overall StudyBecame pregnant during gap in treatment after pregnancy loss01
Overall Studyfound ineligible after randomization11
Overall StudyLost to Follow-up22
Overall Studyunable to complete study due to personal constraints10
Overall StudyWithdrawal by Subject20

Baseline characteristics

CharacteristicLetrozoleLetrozole + Clomiphene CitrateTotal
Age, Continuous30.7 years
STANDARD_DEVIATION 4.25
29.9 years
STANDARD_DEVIATION 4.31
30.2 years
STANDARD_DEVIATION 4.28
BMI36.24 kg/m^2
STANDARD_DEVIATION 7.97
36.78 kg/m^2
STANDARD_DEVIATION 7.91
36.50 kg/m^2
STANDARD_DEVIATION 7.92
Race/Ethnicity, Customized
Asian
4 Participants2 Participants6 Participants
Race/Ethnicity, Customized
Black non-hispanic
3 Participants1 Participants4 Participants
Race/Ethnicity, Customized
Hispanic
10 Participants7 Participants17 Participants
Race/Ethnicity, Customized
Multiple
1 Participants2 Participants3 Participants
Race/Ethnicity, Customized
Other
1 Participants1 Participants2 Participants
Race/Ethnicity, Customized
White non-hispanic
79 Participants79 Participants158 Participants
Region of Enrollment
United States
98 participants92 participants190 participants
Sex: Female, Male
Female
98 Participants92 Participants190 Participants
Sex: Female, Male
Male
0 Participants0 Participants0 Participants

Adverse events

Event typeEG000
affected / at risk
EG001
affected / at risk
deaths
Total, all-cause mortality
0 / 980 / 92
other
Total, other adverse events
68 / 9869 / 92
serious
Total, serious adverse events
2 / 982 / 92

Outcome results

Primary

Ovulation

Number of Participants with Mid-luteal serum progesterone level \>=3 ng/ml Number of cycles with Mid-luteal serum progesterone level \>=3 ng/ml

Time frame: Tested 6 to 8 days following patient reporting a positive ovulation test (LH surge). If no surge is detected, progesterone lab will be drawn on Cycle day 21-24.

ArmMeasureValue (COUNT_OF_PARTICIPANTS)
LetrozoleOvulation91 Participants
Letrozole + Clomiphene CitrateOvulation89 Participants
Secondary

Clinical Pregnancy

intrauterine pregnancy with fetal heart motion determined by ultrasound

Time frame: 6 to 7 weeks after treatment in treatment cycles 1, 2, and 3 (treatment cycle is 24-35 days depending on ovulation)

Secondary

Conception

positive serum or urinary test of hCG

Time frame: 5 weeks after treatment in treatment cycles 1, 2, and 3 (treatment cycle is 24-35 days depending on ovulation)

Secondary

Endometrial Thickness

Endometrial thickness assessed by ultrasound

Time frame: Cycle day 21-24 of 3rd treatment cycle

Population: Participants who completed study ultrasound during their 3rd study treatment cycle

ArmMeasureValue (MEAN)Dispersion
LetrozoleEndometrial Thickness9.11 mmStandard Deviation 3.11
Letrozole + Clomiphene CitrateEndometrial Thickness9.41 mmStandard Deviation 2.79
Secondary

Endometrial Thickness

Endometrial thickness assessed by ultrasound

Time frame: Cycle day 21-24 of 1st treatment cycle

Population: Participants completing study ultrasound during their first study treatment cycle

ArmMeasureValue (MEAN)Dispersion
LetrozoleEndometrial Thickness8.52 mmStandard Deviation 3.08
Letrozole + Clomiphene CitrateEndometrial Thickness9.41 mmStandard Deviation 3.1
Secondary

Endometrial Thickness

Endometrial thickness assessed by ultrasound

Time frame: Cycle day 21-24 of 2nd treatment cycle

Population: Participants who completed study ultrasound during their 2nd study treatment cycle

ArmMeasureValue (MEAN)Dispersion
LetrozoleEndometrial Thickness9.15 mmStandard Deviation 3.09
Letrozole + Clomiphene CitrateEndometrial Thickness9.32 mmStandard Deviation 2.81
Secondary

Live Birth

delivery of a live born infant determined by medical record abstraction

Time frame: 9-10 months following final treatment cycle (treatment cycle is 24-35 days depending on ovulation)

Secondary

Multiple Birth

delivery of more than one infant determined by medical record abstraction

Time frame: 9-10 months following final treatment cycle (treatment cycle is 24-35 days depending on ovulation)

Secondary

Multiple Gestation

intrauterine pregnancy with more than one fetal heart motion determined by ultrasound

Time frame: 6 to 7 weeks after treatment in treatment cycles 1, 2, and 3 (treatment cycle is 24-35 days depending on ovulation)

Secondary

Number of Corpora Lutea

Number of corpora lutea on ultrasound

Time frame: Cycle day 21-24 of 3rd treatment cycle

Population: Participants who completed a study ultrasound during their 3rd treatment cycle.

ArmMeasureValue (MEAN)Dispersion
LetrozoleNumber of Corpora Lutea0.99 number of corpora luteaStandard Deviation 0.75
Letrozole + Clomiphene CitrateNumber of Corpora Lutea1.22 number of corpora luteaStandard Deviation 0.9
Secondary

Number of Corpora Lutea

Number of corpora lutea on ultrasound

Time frame: Cycle day 21-24 of 1st treatment cycle

Population: Participants who completed study ultrasound during c1st study treatment cycle.

ArmMeasureValue (MEAN)Dispersion
LetrozoleNumber of Corpora Lutea0.64 number of corpora luteaStandard Deviation 0.68
Letrozole + Clomiphene CitrateNumber of Corpora Lutea1.09 number of corpora luteaStandard Deviation 1.02
Secondary

Number of Corpora Lutea

Number of corpora lutea on ultrasound

Time frame: Cycle day 21-24 of 2nd treatment cycle

Population: Participants who completed a study ultrasound in their 2nd study treatment cycle.

ArmMeasureValue (MEAN)Dispersion
LetrozoleNumber of Corpora Lutea0.92 number of corpora luteaStandard Deviation 0.7
Letrozole + Clomiphene CitrateNumber of Corpora Lutea1.07 number of corpora luteaStandard Deviation 0.78
Secondary

Pregnancy Loss

biochemical pregnancy, miscarriage, or ectopic pregnancy determined by ultrasound or medical record abstraction

Time frame: Through study completion, an average of 1 year

Source: ClinicalTrials.gov · Data processed: Feb 4, 2026