The primary objective of this study will evaluate the safety and tolerability of single, escalating doses of PF-04958242 administered orally to healthy adult participants. This study will also evaluate the plasma pharmacokinetics (PK) of single doses of PF-04958242 after single escalating doses of PF-04958242 administered orally to healthy adult participants.

This study was previously posted by Pfizer, Inc. Sponsorship of the trial was transferred to Biogen.

Key Inclusion Criteria:

• Body Mass Index (BMI) of 17.5 to 30.5 kilograms per meter quared (kg/m2);
• Total body weight >50 kilograms (kg) (110 pounds [lbs]);

Key Exclusion Criteria:

• Evidence or history of clinically significant hematological, renal, endocrine, pulmonary, gastrointestinal, cardiovascular, hepatic, psychiatric, neurologic, or allergic disease (including drug allergies, but excluding untreated, asymptomatic, seasonal allergies at time of dosing);
• Positive urine drug screen;
• Pregnant or nursing females, and females of child bearing potential;
• Severe acute or chronic medical or psychiatric condition or laboratory abnormality that may increase the risk associated with study participation or investigational product administration or may interfere with the interpretation of study results and, in the judgment of the investigator, would make the participant inappropriate for entry into this study.

NOTE: Other protocol defined Inclusion/Exclusion criteria may apply