The goal of this clinical trial is to assess the safety, tolerability and blood levels following a single dose or after multiple doses of CK-0045 given subcutaneously to healthy participants or otherwise healthy participants with obesity. 76 participants will receive CK-0045 or matching placebo at different escalating doses in 2 study parts: 40 healthy participants will receive a single dose and 36 otherwise healthy participants with obesity will receive 6 doses one week apart.

Inclusion Criteria:

• For non-vasectomized men with partners who are women of child bearing potential (WOCBP) and for WOCBP, highly effective contraception for 3 months.
• For all female participants: a negative serum (β-hCG) pregnancy test at screening and a negative urine pregnancy test on Day -1.
• In the opinion of the investigator, healthy based on medical history, physical and neurological examination, vital signs, and ECG, and clinical chemistry, hematology, coagulation, and urinalysis.
• A body weight in the range of 50 to 100 kg and a body mass index (BMI) of 18.5 to 27.0 kg/m2, inclusive, at screening for the SAD part and a BMI of 30.0 to 39.9 kg/m2, inclusive, at screening for the MAD part.
• A systolic blood pressure of ≥91 and ≤140 mmHg (SAD) / ≤145 mmHg (MAD) , a diastolic blood pressure of ≥51 and ≤80 mmHg (SAD) / ≤90 mmHg (MAD), and a pulse rate of ≥45 and ≤100 bpm at screening and Day 1 predose.
• Negative COVID-19 test (PCR) and no clinical symptoms of corona on Day -1.
• Signed informed consent form.
• Willing to adhere to the prohibitions and restrictions specified in the protocol.

Exclusion Criteria:

• Currently have or have a history of any clinically significant medical illness or medical disorders the investigator considers should exclude the participant.
• Have one or more clinical laboratory test values outside the normal range at screening or on Day -1 (exceptions apply to MAD for fasting glucose, triglycerides, total cholesterol and liver enzymes).
• Has a QTcF interval >430 ms at screening or Day 1 predose for the SAD part or has a QTcF interval >450 ms (for male participants) or >470 ms (for female participants) at screening or Day 1 predose for the MAD part.
• Have a clinically significant or chronic infection or diagnosed latent infection.
• Significant acute illness within 7 days prior to the (first) study drug administration or have had a major illness or hospitalization within 1 month prior to the (first) study drug administration.
• Any history of clinically relevant skin diseases including but not limited to: Psoriasis, vitiligo, atopic dermatitis, eczema.
• History of any malignancy.
• Tattoos present on place of injection site.
• Major or traumatic surgery within 6 months of screening.
• Any participant who plans to undergo elective surgery within 4 weeks prior to the (first) study drug administration and through the end of the study.
• Positive serology test for HIV type 1 and 2 antibodies, hepatitis B surface antigen (HBsAg), or hepatitis C virus (HCV) antibodies at screening.
• Recent history (within 6 months from screening) of alcohol or drug abuse.
• Active smoker and/or has used nicotine or nicotine-containing products (including e cigarettes or the equivalent of e-cigarettes) within the past 6 months of the (first) study drug administration.
• A positive urine toxicology screen at screening or Day -1 for substances of abuse.
• Have a positive alcohol breath test at screening or Day -1.
• Consumes, on average, more than approximately 500 mg/day of caffeine at screening for the SAD part or consumes, on average, more than approximately 700 mg/day of caffeine at screening for the MAD part.
• Donated blood within 90 days prior to (first) study drug administration.
• Trains/exercises intensively, e.g., for a marathon or triathlon, or at a competitive level.
• Have a history of active drug and/or food allergy or other active allergic disease requiring the constant use of medications, or a history of severe allergic reaction, angioedema or anaphylaxis at screening.
• Received any experimental therapy or new investigational agent within 30 days or 5 half-lives (whichever is longer) of the (first) study drug administration.
• Treatment with over-the-counter medications, and herbal medication within 14 days or prescription medications within 14 days or 5 half-lives (whichever is longer) prior to (first) study drug administration and through the end of the study, unless approved by the investigator.