Could a new drug help babies with a common but dangerous birth infection?

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: 1. Signed informed consent from parent(s) or legal guardian(s) 2. Cytomegalovirus (CMV) confirmation by culture, shell vial, or Polymerase Chain Reaction (PCR) tests from a specimen obtained at \</= 30 days of life from saliva, blood, or urine 3. Symptomatic congenital CMV disease\* 4. Age at study enrollment: 1. \</= 83 days for Group 1 subjects\*\* 2. \</= 90 days for Group 2 subjects 5. Weight at study enrollment 2.6 kg to \< 8.0 kg 6. Gestational age \>/= 32 weeks at birth 7. Intention by patient's physician to clinically treat infant with oral valganciclovir for 6 months for symptomatic congenital CMV disease * Manifested by one or more of the following: thrombocytopenia; petechiae; hepatomegaly; splenomegaly; intrauterine growth restriction; hepatitis; or Central Nervous System (CNS) involvement such as microcephaly, radiographic abnormalities indicative of CMV CNS disease, abnormal cerebrospinal fluid (CSF) indices for age, chorioretinitis, hearing deficits as detected by formal brainstem evoked response, and/or positive CMV Polymerase Chain Reaction (PCR) from CSF \*\*Group 1 subjects must enroll and receive the Dose Finding Day dose of letermovir on or before 83 days of life so that oral valganciclovir can be started prior to 12 weeks 6 days (which is 90 days) of life, as is standard of care. For this study, the date of birth is counted as day of life 0 Exclusion Criteria: 1. Imminent demise 2. Infants known to be born to women who are HIV positive (but HIV testing is not required for study entry) 3. Current receipt of other investigational drugs 4. Grade 3 or 4 alanine aminotransferase (ALT) utilizing Division of AIDS (DAIDS) Toxicity Table 5. Grade 3 or 4 total bilirubin utilizing DAIDS Toxicity Table 6. Gastrointestinal abnormality which might preclude absorption of an oral medication (e.g., a history of necrotizing enterocolitis) 7. Anticipated concomitant administration of carbamazepine (Tegretol), nafcillin, phenobarbital, or phenytoin (Dilantin) during the period of study drug administration