Inclusion Criteria:
* Male participants, aged 18 to 65 years (inclusive) at the time of informed consent.
* In good general health (Investigator judgement) with no significant medical history and no clinically significant abnormalities on physical examination, vital signs, or 12-lead ECG - including systolic blood pressure 110-140 mmHg (inclusive) at Screening and Day -1 - at Screening and/or before first IP administration.
* BMI ≥ 18.0 and ≤ 32.0 kg/m² and weight ≥ 50 kg.
* Nonsmoker or casual smoker (\< 5 cigarettes/week equivalent) with no tobacco use within 2 months prior to Screening (Investigator discretion).
* Clinical laboratory values within normal range (or not clinically significant per Investigator).
* Fertile men agree to acceptable contraception from Screening until 90 days after last IP dose, and no sperm donation from first dose until ≥ 90 days after last dose.
* Able and willing to attend required study visits.
* Able and willing to provide written informed consent before any study procedures.
Exclusion Criteria:
* Physical or psychological condition that would impair protocol compliance or study completion (Investigator judgement).
* History of, or condition that would contraindicate study medication or interfere with study evaluations (Investigator judgement).
* Previous history of any of: myocardial infarction; cerebrovascular accident; arrhythmia; congestive heart failure; unstable angina; recent (\<6 months) need for calcium-channel/beta-blocker/nitrate/anti-epileptic therapy; uncontrolled hypertension (SBP \>140 or DBP \>100 mmHg); hypotension (SBP \<90 or DBP \<60 mmHg) incl. syncope/orthostatic/vasovagal; pulmonary/pericardial/retroperitoneal fibrotic disorders; sickle-cell disease or trait; cardiac valve disease; severe psychiatric disorders; Raynaud's/vasospastic disorders; bariatric surgery (cholecystectomy acceptable).
* Blood/plasma donation or significant blood loss (450 mL) within 30 days prior to first IP dose.
* Fever (\>38°C) or symptomatic viral/bacterial infection within 2 weeks prior to Screening.
* Infections requiring parenteral antibiotics within 1 month prior to Screening.
* Concomitant use of an indwelling urethral catheter.
* Concomitant nitrates/nitric-oxide donors, potent CYP3A4 inhibitors (e.g. ritonavir, indinavir, ketoconazole) or moderate inhibitors (e.g. erythromycin); unwilling to avoid St. John's wort and CYP3A4-active herbals (e.g. grapefruit) within 14 days prior and throughout the study.
* Medications that significantly affect BP: nitrates (any form), alpha-blockers (e.g. doxazosin, terazosin, tamsulosin), guanylate cyclase stimulators (e.g. riociguat).
* Positive HCV antibody, HBsAg, or HIV antibody.
* Live vaccine within 4 weeks prior to first IP dose.
* Poor pill-swallowing ability or poor venous access.
* History of severe allergic/anaphylactic reactions or sensitivity to IP or constituents.
* History of malignancy (except non-melanoma skin cancer excised \>5 years prior to Screening).
* Clinically significant abnormal Screening ECG (e.g. QRS ≥ 120 msec and/or QTcF \> 450 msec, per Investigator).
* History/evidence of renal disease or eGFR \< 60 mL/min/1.73 m² at Screening (2021 CKD-EPI creatinine equation).
* Immunosuppressive drug exposure (incl. experimental therapies) within 4 months or 5 half-lives (whichever longer) prior to Screening.
* Positive urine toxicology panel (barbiturates, THC, amphetamines/methamphetamines, methadone, MDMA, phencyclidine, tricyclic antidepressants, benzodiazepines, opiates, cocaine) or positive alcohol breath test.
* Unwilling to abstain from alcohol, caffeine and nicotine from 48 h prior to admission, during confinement, and 48 h prior to follow-up visits.
* History of substance abuse/dependency or recreational IV drug use in the last 12 months (self-declared).
* Unwilling to refrain from strenuous exercise (incl. weightlifting) 48 h prior to admission and follow-up visits.
* Anything the Investigator considers would jeopardize participant safety, prevent full participation, or compromise data interpretation.
