The purpose of this two part study is to assess the effect of multiple doses of isavuconazole on the pharmacokinetics of multiple doses of lopinavir/ritonavir and the effect of multiple doses of lopinavir/ritonavir on the pharmacokinetics of isavuconazole.

Part 1 of the study includes 12 subjects randomized to receive either isavuconazole alone or isavuconazole in combination with lopinavir/ritonavir. The purpose of Part 1 is to evaluate safety and tolerability and to establish the effect of multiple doses of lopinavir/ritonavir on isavuconazole.

Part 2, if initiated, includes 54 subjects randomized to receive isavuconazole alone, lopinavir/ritonavir alone, or isavuconazole in combination with lopinavir/ritonavir.

Inclusion Criteria:

• The subject has a body weight of at least 45 kg and has a body mass index (BMI) of 18 to 32 kg/m2, inclusive
• Results for aspartate aminotransferase (AST) and alanine aminotransferase (ALT), total bilirubin, lipase, amylase, glucose and triglycerides must be within the normal range
• The female subject agrees to sexual abstinence, or is surgically sterile, postmenopausal (defined as at least 2 years at Screening without menses), or using a medically acceptable double barrier method (e.g. spermicide and diaphragm, or spermicide and condom) to prevent pregnancy and agrees to continue using this method from Screening until 3 weeks after the follow-up visit at the end of the study; and is not lactating or pregnant as documented by negative pregnancy tests at Screening and Day -1
• The male subject agrees to sexual abstinence, is surgically sterile, or is using a medically acceptable method to prevent pregnancy and agrees to continue using this method from Screening until 3 weeks after the follow-up visit at the end of the study

Exclusion Criteria:

• The subject has a history of unexplained syncope, cardiac arrest, unexplained cardiac arrhythmia or torsade de pointes, structural heart disease, or family history of Long QT syndrome (suggested by sudden death of a close relative at a young age due to possible or probable cardiac causes)
• The subject has a history of pancreatitis
• The subject has a positive result for hepatitis C antibodies, hepatitis B surface antigen at Screening or is known to be positive for human immunodeficiency virus (HIV)
• The subject has a known or suspected allergy to any of the components of the trial products including lopinavir/ritonavir or the azole class of compounds, or a history of multiple and/or severe allergies to drugs or foods (as judged by the investigator), or a history of severe anaphylactic reactions- - The subject is a smoker (any use of tobacco or nicotine containing products) within 6 months prior to Screening
• The subject has had treatment with prescription drugs or complementary and alternative medicines within 14 days prior to Day -1, or over-the-counter medications within 1 week prior to Day -1, with the exception of acetaminophen up to 2 g/day
• The subject has a recent history (within the last 2 years) of drug or alcohol abuse, as defined by the investigator, or a positive drug and/or alcohol screen
• The subject has participated in a previous isavuconazole study