An Early Phase 1 interventional study of YASO GEL and Placebo gel in Early-phase Safety and PK Study of a Vaginal Gel, sponsored by Yaso Therapeutics Corporation. Not yet recruiting at 1 site in United States. Open to participants aged 18 Years to 55 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2025-12-19.
Sponsored by Yaso Therapeutics Corporation · Early Phase 1, Interventional, and Treatment
The goal of this clinical trial is to assess the safety and pharmacokinetics of YASO GEL in healthy adult participants. This is a first-in-human study designed to understand how the gel is absorbed and distributed in plasma and vaginal fluid, and to evaluate the methods used to measure drug levels in humans.
The main questions the study aims to answer are:
What is the preliminary safety and tolerability of YASO GEL at a subtherapeutic 0.7% dose?
How is YASO GEL absorbed and distributed, and does sexual activity affect its pharmacokinetics?
Participants will:
Receive an application of YASO GEL.
Provide blood and vaginal fluid samples for pharmacokinetic analysis.
Participate in a sub-study evaluating the impact of sexual activity on safety and drug exposure.
Additional information on product acceptability, adherence, and exploratory laboratory analyses will be collected to inform the design of future studies.
This study initiates with a first-in-human lead-in study using a subtherapeutic 0.7% dose of YASO GEL. The study aims to provide a preliminary assessment of PPCM pharmacokinetics in plasma and vaginal fluid, and to validate a bioanalytical assay to be used to measure efficacy in both the Phase 1 and sub studies. Data from this study will help ensure that pharmacokinetic sampling is adequate for subsequent clinical trials and will provide initial safety information to support a Phase 1 study.
The subsequent randomized double-blind Phase 1 study will use a therapeutic 2.0% dose of YASO GEL administered once in Stage 1 of the Phase 1 study and once daily for 7 days in Stage 2 of the Phase 1 study. The Phase 1 study is designed to provide comprehensive baseline safety and pharmacokinetic data in a dose response manner. As such, it is important to assess the genitalia (vulva, perineum and vagina for female participants and penis, scrotum, and perineum for male participants) after each dose for safety, initially with single dose and then with repeated dosing. Because it is anticipated that a coitally-dependent product will be applied prior to each act of coitus, and individuals may have coitus more than once a day, future studies will evaluate more frequent dosing and further characterize the YASO GEL safety profile.
Secondarily, acceptability and adherence data will be collected to inform future product design and patient education. Exploratory endpoints include assessment of vaginal fluid samples for vaginal microbiome, soluble immune mediators, ex-vivo contraceptive activity and anti-microbial activity against both HIV and Ng.
A sub-study is included to evaluate the impact of coitus on safety and pharmacokinetics of YASO GEL use. This study will also collect acceptability and adherence data to inform future product design and patient education. Vaginal fluid samples will be assessed for contraceptive activity and ex vivo anti-microbial activity against both HIV and Ng, in an exploratory fashion to inform future study design.
The study will include healthy adult participants. Female participants will apply the gel internally in all studies. Male participants will apply the gel externally in the Lead-in and Phase 1 studies and be exposed to the gel in the coital sub-study. The results from this study will guide the design of future studies and help establish the safety and efficacy profile of YASO GEL in humans.
224 studies on the registry are indexed under Sexual Behavior; 30 are open to participants now.
This study's planned enrollment of 72 is below the median of 264 across 179 interventional studies indexed under Sexual Behavior.
Browse Sexual Behavior studies →This is the only study on the registry with Yaso Therapeutics Corporation as lead sponsor.
Counted across the registry records on this site, refreshed daily.
Inclusion Criteria:
Individuals who meet the following criteria are eligible for inclusion in the study (see additional gender specific criteria at the end of the section):
Adults who are:
Female specific criteria:
Using an effective method of contraception and intending to continue use of an effective method for the duration of study participation. Acceptable methods are:
Male specific criteria:
a. Must agree to abstain from:
4.1.2 Inclusion Criteria - Sub-Study
Heterosexual couples who meet the following criteria are eligible for inclusion in the study:
Couple-level criteria:
Female specific inclusion criteria:
Using an effective method of contraception and intending to continue use of an effective method for the duration of study participation. Acceptable methods are:
Male specific inclusion criteria:
Must agree to abstain from
Exclusion Criteria:
General exclusions:
Laboratory abnormalities at screening:
Note: Grade is per Version 2.1 of the DAIDS Toxicity Table
Calculated Grade 2 or higher (i.e., ≤ 90 mL/minute using the Cockcroft-Gault equation.
(140 - age in yrs) x (weight in kg) x (0.85)/72 x (serum Cr in mg/dL)
Female specific exclusion criteria:
Note: Cervical bleeding associated with speculum insertion and/or specimen collection judged to be within the range of normal according to the clinical judgment of the IoR/designee is considered expected non-menstrual bleeding and is not exclusionary.
Note: Otherwise, eligible participants with exclusionary pelvic exam findings may be enrolled/randomized after the findings have improved to a non-exclusionary severity grading or resolved within 60 days of providing informed consent for screening.
Male specific exclusion criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
A condition in which the immune system attacks the body’s own tissues, such as rheumatoid arthritis, lupus, psoriasis, type 1 diabetes or inflammatory bowel disease.
Immunotherapy studies often leave out active autoimmune disease, and some name exceptions, such as thyroid disease on replacement hormone. Check the exceptions this study lists.
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
The protein in red blood cells that carries oxygen. A low level is anaemia, which can cause tiredness and breathlessness. Measured in g/dL or g/L (9 g/dL is 90 g/L).
Two enzymes measured in a routine blood test of the liver. Higher levels can mean the liver is under strain or damaged. SGPT and SGOT are older names for ALT and AST.
Criteria usually give a limit as a multiple of the upper limit of normal (ULN), often higher when cancer has spread to the liver.
The top of the normal range for a blood test, as set by the laboratory that runs it. Each lab prints its own range next to your result.
“≤ 2.5 × ULN” means the result can be up to two and a half times that top value.
How quickly the kidneys clear creatinine, a waste product, from the blood. A study may estimate it from a blood test with age, weight and sex (often by the Cockcroft–Gault formula), or measure it using blood and urine collected over a set time. Given in mL/min; higher is better.
A biopsy takes a small piece of tissue to examine. “Archival tissue” is a sample already taken, for example at diagnosis, and kept by the hospital.
Whether a stored sample will do depends on when it was taken, how much there is and what the study needs. Ask whether the study accepts your stored sample or needs a new biopsy.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraception
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Autoimmune disease
A condition in which the immune system attacks the body’s own tissues, such as rheumatoid arthritis, lupus, psoriasis, type 1 diabetes or inflammatory bowel disease.
Immunotherapy studies often leave out active autoimmune disease, and some name exceptions, such as thyroid disease on replacement hormone. Check the exceptions this study lists.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
HIV
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hemoglobin (Hb)
The protein in red blood cells that carries oxygen. A low level is anaemia, which can cause tiredness and breathlessness. Measured in g/dL or g/L (9 g/dL is 90 g/L).
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ALT and AST (liver enzymes)
Two enzymes measured in a routine blood test of the liver. Higher levels can mean the liver is under strain or damaged. SGPT and SGOT are older names for ALT and AST.
Criteria usually give a limit as a multiple of the upper limit of normal (ULN), often higher when cancer has spread to the liver.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ULN (upper limit of normal)
The top of the normal range for a blood test, as set by the laboratory that runs it. Each lab prints its own range next to your result.
“≤ 2.5 × ULN” means the result can be up to two and a half times that top value.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Creatinine clearance (CrCl)
How quickly the kidneys clear creatinine, a waste product, from the blood. A study may estimate it from a blood test with age, weight and sex (often by the Cockcroft–Gault formula), or measure it using blood and urine collected over a set time. Given in mL/min; higher is better.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Biopsy and archival tissue
A biopsy takes a small piece of tissue to examine. “Archival tissue” is a sample already taken, for example at diagnosis, and kept by the hospital.
Whether a stored sample will do depends on when it was taken, how much there is and what the study needs. Ask whether the study accepts your stored sample or needs a new biopsy.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Participants receive a single low dose of the investigational contraceptive to assess initial safety and tolerability.
Drug: YASO GEL
Participants receive a single full-strength dose of the investigational contraceptive in a randomized, double-blind design.
Drug: YASO GEL
Participants receive a single dose of placebo in a randomized, double-blind design.
Drug: Placebo gel
Participants receive daily full-strength doses of the investigational contraceptive for 7 days in a randomized, double-blind design.
Drug: YASO GEL
Participants receive daily placebo doses for 7 days in a randomized, double-blind design.
Drug: Placebo gel
Participants receive full-strength investigational contraceptive in an open-label sub-study to further assess safety and exploratory endpoints.
Drug: YASO GEL
Contraceptive gel
Inactive placebo gel matching the investigational contraceptive
Incidence of treatment-emergent adverse events
Number, type, and severity of adverse events observed from first dose through end of follow-up per study section.
Time frame: Incidence of treatment-emergent adverse events, measured from first dose through Day 3 post-dose (Lead-in), 21 days post-dose (Phase 1, Stage 1), 28 days post first dose (Phase 1, stage 2) and 24 hours post dose (coital sub-study).
Plasma and vaginal fluid concentrations of investigational contraceptive
Concentrations of the investigational contraceptive measured in blood plasma and vaginal fluid at predefined timepoints from first dose through last PK sample per study section.
Time frame: Time from first dose to last PK sample collection per study section: lead-in up to Day 3; Phase 1 Stage 1 up to Day 21; Phase 1 Stage 2 up to Day 28; sub-study up to 24 hours post dose; samples collected at multiple predefined timepoints.
Acceptability Questionnaire
To assess acceptability of IP use
Time frame: Questionnaires administered at Day 2 post-dose during Phase 1, Stage 1 and on the final day of dosing, Day 7 during Phase 1, Stage 2 and immediately after intercourse on Day 3 of the coital sub-study.
Adherence to dosing schedule
Adherence to 7-day dosing schedule based on self-reported use evidenced by participant diaries, device logs, or returned product counts
Time frame: Adherence based on self-reported use evidenced by participant diaries, device logs, or returned product counts post dosing on Day 1 and through Day 7 of the Phase 1, Stage 2 study.
Anti-viral Activity
To define the relationship between the PK profile of IP and predicted HIV anti-viral activity assessed by TZM-bl assay
Time frame: Pre and post-dose on Day 1, Day 2 and Day 7 of Phase 1, Stage 1 and after each coital visit during the sub-study.
Anti-bacterial activity
To define the relationship between the PK profile of IP and predicted Ng anti- bacterial activity assessed by microtitre plate assay
Time frame: Pre and post-dose on Day 1, Day 2 and Day 7 of Phase 1, Stage 1 and after each coital visit during the sub-study.
Hyaluronan Binding Assay (HBA) - Vaginal Fluid Exposed to Study Gel (Ex-Vivo)
Proportion of motile, morphologically normal sperm that bind to hyaluronan when applied to vaginal fluid samples that have been collected and then incubated with the study gel ex-vivo (laboratory simulation of product exposure). Samples will be prepared according to validated lab procedures and assessed by light microscopy.
Time frame: Pre and post dose day 1, Day 2 and Day 7 of Phase 1, Stage 1
Nugent Score
To assess the impact of IP on vaginal microbiota morphology
Time frame: Pre dose on Day 1 and on Day 7 of Phase 1, Stage 1 and Day 1 and Day 7 of Phase 1, Stage 2
Premature acrosomal loss (PAL) assay
The Premature Acrosomal Loss (PAL) assay evaluates whether exposure to the study product induces premature acrosome exocytosis in human sperm. Sperm samples are incubated with the test article and then stained with a fluorescent acrosome marker (e.g., FITC-PSA or FITC-PNA) to assess acrosomal integrity. The proportion of sperm exhibiting acrosomal loss is quantified by microscopy or flow cytometry and compared with control conditions.
Time frame: After intercourse on Day 2 and Day 3 of the coital sub-study.
Vaginal Microbiome
Assessment of the vaginal microbiota using validated culture methods and quantitative PCR (qPCR) assays to detect and quantify key vaginal microbial groups associated with vaginal health.
Time frame: Pre-dose on Day 1 and on Day 7 of the Phase 1, Stage 1 and on Day 1, Day 7, Day 14 and Day 21 of Phase 1, stage 2.
Vaginal Inflammatory Biomarkers
Concentrations of selected soluble immune mediators in vaginal fluid, assessed using validated laboratory immunoassays.
Time frame: Pre-dose on Day 1 and Day 7 of Phase 1, Stage 1 and Day 1, Day 7, Day 14 and Day 21 of Phase 1, stage 2.
Sperm Microscopy (Motility, Morphology, Vitality)
Sperm microscopy will be performed to assess key semen parameters, including motility, morphology, concentration, and vitality, following WHO laboratory standards.
Time frame: After intercourse on Day 2 and Day 3 of the coital sub-study.
Eosin-Nigrosin Vitality Stain
Eosin-Nigrosin (EN) staining will be used to assess sperm viability.
Time frame: After intercourse on Day 2 and Day 3 of the coital sub-study.
Hyaluronan Binding Assay (HBA)
The Hyaluronan Binding Assay (HBA) measures the proportion of mature, functionally competent sperm capable of binding to hyaluronan, a component of the cumulus oophorus. Sperm are applied to a hyaluronan-coated slide, and the proportion of motile, morphology-normal sperm that bind is quantified.
Time frame: After intercourse on Day 2 and Day 3 of the coital sub-study.
Plan to share: No — External laboratories will perform assays as part of the study; no plans to share individual participant data outside the study team at this time.
No publications or documents are linked to this record.
Start is estimated for Apr 2026; primary completion for Feb 2028, 22 months later.
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This study is not yet recruiting, as verified in Dec 2025. You cannot join it, but the record below documents what was studied.
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