Inclusion Criteria:
* Provides written informed consent and is willing and able to comply with all protocol requirements.
* Healthy male, 18 to 45 years of age, inclusive, on the date of informed consent.
* Body weight 50 to 80 kg, inclusive, and body mass index 19.0 to 26.0 kg/m², inclusive.
* Has no reproductive plans during the study and for 3 months after the last dose; agrees to use effective contraception and not donate sperm during this period.
Exclusion Criteria:
* History of autoimmune disease.
* History of malignancy, except successfully resected cutaneous squamous cell carcinoma, basal cell carcinoma, or localized cervical carcinoma in situ without evidence of metastasis.
* Positive test for human immunodeficiency virus antibody, hepatitis B surface antigen, hepatitis B e antigen, hepatitis C virus antibody, or Treponema pallidum antibody.
* Known history of recurrent or chronic infection, including but not limited to chronic renal infection, chronic chest infection such as bronchiectasis, sinusitis, recurrent urinary tract infection, or an open, draining, or infected skin wound.
* Acute infection within 2 weeks before screening.
* Opportunistic infection within 6 months before screening, including herpes zoster or active cytomegalovirus, Pneumocystis, Histoplasma, Aspergillus, or mycobacterial infection.
* Known history of tuberculosis, clinical findings suspicious for tuberculosis, or a positive tuberculosis laboratory test.
* History of chronic or serious disease, or current disease, involving the respiratory, cardiovascular, digestive, urinary, hematologic, endocrine, immune, neurologic, or psychiatric systems, or otherwise considered unsuitable by the investigator.
* Allergic constitution, including a history of severe drug allergy or hypersensitivity, a definite allergy history, or allergy to either study drug or its components; untreated asymptomatic seasonal allergy or an isolated positive skin test is not exclusionary.
* Any surgery within 6 months before screening or planned surgery during the study.
* Blood loss or donation of at least 400 mL within 3 months before screening, or at least 200 mL within 1 month before screening, or receipt of a blood transfusion within 3 months before screening.
* Clinically significant abnormality in physical examination, vital signs, laboratory tests, 12-lead electrocardiogram, abdominal ultrasonography, or chest radiography during screening.
* History of illicit drug use or drug abuse within 1 year before screening, or a positive drug screen.
* Habitual alcohol or tobacco use (an average of at least 14 units of alcohol per week within 6 months before screening, where 1 unit equals 285 mL beer, 25 mL spirits, or 100 mL wine; or an average of at least 5 cigarettes per day) and inability to abstain during the study.
* Previous use of ipilimumab or an ipilimumab biosimilar.
* Use of any medication within 2 weeks before the first study dose or within 5 half-lives of the medication, whichever is longer, or planned use of other medication during the study, including prescription or nonprescription drugs, Chinese herbal medicines, and dietary supplements.
* Participation in a drug or medical-device clinical trial within 3 months before screening, ongoing follow-up in another clinical study, or exposure within 5 half-lives of the prior investigational drug, whichever is longer.
* Receipt of a live vaccine within 6 months before screening or planned receipt of a live vaccine during the study.
* History of needle or blood phobia, difficult blood collection, or inability to tolerate venipuncture.
* Any other factor considered by the investigator to make participation unsuitable, or withdrawal for the participant's own reasons.
