A First-in-Human, randomized, double-blind, placebo-controlled ascending dose study to assess safety, tolerability, pharmacokinetics and pharmacodynamics of STR-324 in healthy subjects.

1. Signed informed consent prior to any study-mandated procedure
2. Healthy male subjects, 18 to 45 years of age, inclusive at screening.
3. Body mass index (BMI) between 18 and 30 kg/m2, inclusive at screening, and with a minimum weight of 50 kg.
4. All males must practice effective contraception during the study and be willing and able to continue contraception for at least 90 days after their last dose of study treatment.
5. Has the ability to communicate well with the Investigator in the Dutch language and willing to comply with the study restrictions.

1. Evidence of any active or chronic disease or condition that could interfere with, or for which the treatment of might interfere with, the conduct of the study, or that would pose an unacceptable risk to the subject in the opinion of the investigator [(following a detailed medical history, physical examination, vital signs (systolic and diastolic blood pressure, pulse rate, body temperature), 12-lead electrocardiogram (ECG)]. Minor deviations of laboratory values from the normal range may be accepted, if judged by the Investigator to have no clinical relevance.
2. Clinically significant abnormalities, as judged by the investigator, in laboratory test results (including hepatic and renal panels, complete blood count, chemistry panel, coagulation and urinalysis). In the case of uncertain or questionable results, tests performed during screening may be repeated before randomization to confirm eligibility or judged to be clinically irrelevant for healthy subjects.
3. Abnormal renal function (eGFR (MDRD) < 60 v
4. Previous history of seizures or epilepsy.
5. Acute disease state (e.g. nausea, vomiting, fever, or diarrhea) within 7 days before the first study day.
6. Positive Hepatitis B surface antigen (HBsAg), Hepatitis B antibodies, Hepatitis C antibody (HCV Ab), or human immunodeficiency virus antibody (HIV Ab) at screening.
7. Systolic blood pressure (SBP) greater than 140 or less than 90 mm Hg, and diastolic blood pressure (DBP) greater than 90 or less than 50 mm Hg measured in supine position at screening.
8. Abnormal findings in the resting ECG at screening defined as:
- QTcF> 450 or < 300 msec
- Notable resting bradycardia (HR < 45 bpm) or tachycardia (HR > 100 bpm)
- Evidence of atrial fibrillation, atrial flutter, complete branch block, Wolf-Parkinson-White Syndrome, or cardiac pacemaker
9. Use of any medications (prescription or over-the-counter [OTC]), within 14 days of study drug administration, or less than 5 half-lives (whichever is longer). Limited use of non-prescription medications that are not believed to affect subject safety or the overall results of the study may be permitted on a case-by-case basis following approval by the sponsor. No exceptions will be made for known analgesics (e.g. paracetamol or ibuprofen)
10. Use of any vitamin, mineral, herbal, and dietary supplements within 7 days of study drug administration, or less than 5 half-lives (whichever is longer). Exceptions will only be made if the rationale is clearly documented by the investigator.
11. Participation in an investigational drug or device study within 3 months prior to first dosing.
12. History of abuse of addictive substances (alcohol, illegal substances) or current use of more than 21 units alcohol per week, drug abuse, or regular user of sedatives, hypnotics, tranquillizers, or any other addictive agent.
13. Positive test for drugs of abuse at screening or pre-dose.
14. Positive alcohol breath test at screening or pre-dose. Alcohol will not be allowed from at least 24 hours before screening or pre-dose.
15. Smoker of more than 5 cigarettes per day prior to screening or who use tobacco products equivalent to more than 5 cigarettes per day and unable to abstain from smoking whilst in the unit.
16. Is demonstrating excess in xanthine consumption (more than eight cups of coffee or equivalent per day)
17. Any confirmed significant allergic reactions (urticaria or anaphylaxis) against any drug, or multiple drug allergies (non-active hay fever is acceptable).
18. Loss or donation of blood over 500 mL within three months prior to screening or intention to donate blood or blood products during the study.
19. Any known factor, condition, or disease that might interfere with treatment compliance, study conduct or interpretation of the results such as drug or alcohol dependence or psychiatric disease.
20. Any current, clinically significant, known medical condition in particular any existing conditions that would affect sensitivity to cold (such as atherosclerosis, Raynaud*s disease, urticaria, hypothyroidism) or pain (disease that causes pain, hypesthesia, hyperalgesia, allodynia, paraesthesia, neuropathy, etc.);
21. Subjects indicating pain tests intolerable at screening or achieving tolerance at >80% of maximum input intensity for any pain test for cold, pressure and electrical tests;;Additional exclusion criteria (Part 2 (groups 4 and 5))
22. History or presence of post-inflammatory hyperpigmentation;
23. Dark skin (Fitzpatrick skin type IV, V or VI), widespread acne, freckles, tattoos or scarring on the back;
24. A MED higher than 355 mJ/cm2 at screening.