To Assess Safety, Tolerability and PK of NEX-20A, a Subcutaneous Prolonged-release Injection to Healthy Subjects

Inclusion Criteria:

1. Willing and able to give written informed consent for participation in the study.
2. Healthy male subject aged 18 to 65 years, inclusive.
3. Clinically normal medical/surgical history, physical findings, vital signs, 12-lead electrocardiograms (ECGs) and safety laboratory values at the time of screening, as judged by the Investigator.
4. Prospective (male) subjects who are sexually active with female partners must agree to use condoms as well as one of the following highly effective (failure rate \<1%) methods of contraception with their partner(s) from 14 days prior to the time of NEX-20A administration until 90 days after the follow-up/end-of-study visit (Visit 14).

   * Previous male sterilization, defined as vasectomy conducted at least 6 months prior to screening with appropriate post-vasectomy documentation of the absence of sperm cells in the ejaculate.
   * Previous female sterilization, defined as tubal ligation or permanent bilateral occlusion of fallopian tubes.
   * Oral (except low-dose gestagen \[lynestrenol and norethisterone\]), injectable or implanted hormonal contraceptive associated with the inhibition of ovulation.
   * Intrauterine device (IUD).
   * Intrauterine hormone-releasing system (IUS), e.g., progestin-releasing coil

Exclusion Criteria:

1. Body weight outside body mass index 18-30 kg/m2
2. Subjects who intend to father a child during the course of the study, i.e., from screening to the final pregnancy check at Visit 15, or whose female partner is pregnant or currently breastfeeding.
3. Regular smoking or use of nicotine products within the past 6 months prior to screening.

   Irregular use of nicotine (e.g., smoking, snuffing, chewing tobacco) less than 3 times/week before the screening visit will be allowed.
4. Any intake of alcohol within the previous 24 hours of screening or subsequent study visits, according to alcohol urine tests.
5. Any positive screen for drugs of abuse at screening or subsequent study visits.
6. Any positive result on screening for serum hepatitis B surface antigen, hepatitis C antibodies or human immunodeficiency virus (HIV), according to diagnostic tests.
7. Any use of prescription medication within the previous 14 days of the administration of NEX-20A, at the discretion of the Investigator.
8. Any use of over the counter (non-prescription) medication within the previous 48 hours of the administration of NEX-20A, at the discretion of the Investigator, except occasional intake of paracetamol (maximum 2000 mg/day), as well as nasal decongestants without cortisone, antihistamine or anticholinergics.
9. Regular use of any herbal remedies, vitamins, minerals, and other food supplements, at the discretion of the Investigator, within the previous 14 days of the administration of NEX-20A.
10. Malignancy within the past 5 years, with the exception of in situ removal of basal cell carcinoma.
11. Dermatological conditions, tattoos or large scars on the abdomen, thigh or upper arm which, in the opinion of the Investigator, may limit the evaluation of local tolerability.
12. History of or current thromboembolic disease, including but not limited to deep vein thrombosis (DVT) and other venous thromboembolisms, untreated hypertension and/or untreated hyperlipidaemia, as judged by the Investigator.
13. Family history of thromboembolic disease, specifically first-degree relative with history of or current thromboembolic disease (see exclusion criterion 12), as judged by the Investigator.
14. History of or current hematologic disorder, including but not limited to thrombocytopenia and/or neutropenia, as judged by the Investigator.
15. History of severe allergy/hypersensitivity or ongoing allergy/hypersensitivity, as judged by the Investigator, or history of hypersensitivity to lenalidomide or drugs with a similar chemical structure or class or to any other ingredient of the formulation/vehicle.
16. History of any clinically significant disease or disorder which, in the opinion of the Investigator, may either put the subject at risk because of participation in the study, or influence the results or the subject's ability to participate in the study.
17. Any clinically significant illness, medical/surgical procedure or trauma within 4 weeks prior to the treatment visit (Visit 2).
18. Any planned major surgery within the duration of the study.
19. After 10 minutes supine rest at the time of screening, any vital signs outside the following ranges:

    * Systolic blood pressure: \<90 or \>140 mmHg, or
    * Diastolic blood pressure \<50 or \>90 mmHg, or
    * Pulse \<40 or \>90 bpm
20. Prolonged QTcF (\>450 ms), cardiac arrhythmias or any clinically significant abnormalities in the resting ECG at the time of screening, as judged by the Investigator.
21. Bilirubin \>25 µmol/L, alanine aminotransferase (ALT) \>1.1 µkat/L, and/or aspartate aminotransferase (AST) \>0.75 µkat/L at the time of screening (all values 1x upper limit of normal \[ULN\]).
22. Estimated glomerular filtration rate (eGFR) \<80 mL/min/1.73 m2 (determined from plasma creatinine by the revised Lund-Malmö GFR estimating equation) at the time of screening.
23. Haemoglobin \<130 g/L, absolute neutrophil count (ANC) \<1.3x109/L, and/or platelet count \<150x109/L at the time of screening.
24. History of or current alcohol abuse or excessive intake of alcohol, as judged by the Investigator.
25. History of or current drug abuse, as judged by the Investigator.
26. History of or current use of anabolic steroids, as judged by the Investigator.
27. Participation in any other clinical study and/or treatment with another investigational drug within 90 days of the treatment visit (Visit 2).
28. Plasma donation within 1 month of screening or blood donation (or corresponding blood loss) during the last 90 days prior to screening.
29. Lack of suitability for participation in the study, for any reason, in the opinion of the Investigator.