The purpose of this study is to evaluate the safety and tolerability of a single subcutaneous (SC) dose of JNJ-26366821.

Inclusion Criteria:

• Overall good health, on the basis of full physical examination, medical history, vital signs, and 12-lead electrocardiogram (ECG) performed at screening
• Body weight 50 - 100 kilogram (kg), body mass index (BMI) 18 - 30 kilogram per meter square (kg/m^2), inclusive at screening
• Platelet count within range: 145 to 350*10^9/liter (L), inclusive at screening
• Hematologic values, coagulation profile, renal and liver function within normal range at screening or if out of range and considered not clinically significant by the investigator
• Non-smoker for at least the previous 3 months prior to screening and negative urine cotinine test at screening and admission

Exclusion Criteria:

• History of any clinically significant medical illness or disorders the investigator considers should exclude the participant, including (but not limited to), neuromuscular, hematological disease, immune deficiency state, respiratory disease, hepatic or gastrointestinal disease, neurological or psychiatric disease, ophthalmological disorders, neoplastic disease, renal or urinary tract diseases, or dermatological disease
• Has a disease or disease treatment history associated with immune suppression or lymphopenia, these include but are not limited to bone marrow or organ transplantation, lymphoproliferative disorders, T- or B-cell deficiency syndromes, splenectomy, functional asplenism, and chronic granulomatous disease
• Has a personal history of genetic or congenital prothrombotic condition or new conditions associated with thromboembolic events or bleeding disorders, including (but not limited to) myocardial infarction, cerebral vascular accident/stroke, deep vein thrombosis, pulmonary embolism, hemophilia, or menometrorrhagia
• Participants who had received hematopoietic growth factors within 3 months prior to study drug administration
• Donation of blood or blood components within 90 days prior to drug administration

The data sharing policy of the Janssen Pharmaceutical Companies of Johnson & Johnson is available at www.janssen.com/clinical-trials/transparency.

As noted on this site, requests for access to the study data can be submitted through Yale open Data Access (YODA) Project site at yoda.yale.edu