A Clinical Trial Evaluating the Efficacy and Safety of Leflutrozole on Testicular Function

Inclusion Criteria: * Signed informed consent form prior to any-related trial activity. * Adult men aged 18-49 years (both inclusive). * Low serum total testosterone concentration on two occasions. * Serum estradiol (E2) level within or above normal range at screening. * Serum Luteinizing Hormone level within or below normal range at screening. * Low total motile sperm count in two samples. * Semen volume ≥1.0 mL in two samples. * Ability to understand and comply with the requirements of the protocol. Exclusion Criteria: * Anatomical abnormalities of the testes or malignant or benign tumors of the testes. * Pituitary or hypothalamic disease. * Prostate disease. * Treatment with one or more of the following prescription drugs or over-the-counter medications or supplements for 6 months prior to the screening visit: 1. Compounds with androgenic or estrogenic properties (i.e., agonist or antagonist) or that affect production of sex hormones. 2. 5-α reductase inhibitors, e.g., finasteride and dutasteride. 3. Fertility drugs, including clomiphene, FSH, hMG and hCG preparations. 4. Growth hormone. 5. Opioid-receptor antagonists, e.g., naloxone and long-acting opioids. 6. Selective α-adrenergic-receptor antagonists (alpha blockers). 7. Topical or systemic testosterone replacement therapy (TRT). 8. Anabolic steroids. * Inability to reliably produce the required semen samples for trial assessments due to significant erectile dysfunction, anorgasmia, or other reasons. * Participation in any clinical trial using clinical intervention within 3 months before the screening visit or 5 half-lives of investigational product administration, whichever is shorter. * Any clinically significant 12-lead ECG abnormalities at screening. * Known history of thromboembolic disease. * Grade 3 lower extremity edema. * Known cardiovascular disease. * Known history of osteoporosis or fragility fractures. * Known moderate or severe impairment of renal or hepatic function. * Untreated diagnosis of sleep apnea. * History of cancer within the last 5 years. * Known alcohol and/or drug abuse within the last 12 months prior to randomization or evidence of such abuse indicated by the laboratory results during the screening assessments. * Known chronic opioid use and/or misuse within the last 12 months prior to randomization. * Any psychiatric or medical disorder or circumstance, which in the investigator's opinion might jeopardize participant's safety or compliance with the protocol. * Hypersensitivity to any active ingredients or excipients in the medicinal products used in this trial.