1) Clarification that subjects in Part A were to be without cirrhosis. 2) Number of subjects was changed from approximately 120 to at least 120, and the minimum number of subjects with prior peginterferon/RBV treatment was increased from 15 to 25. The number of subjects per age group in Part A was clarified to be at least 10 in the older age groups and at least 6 in the youngest age group. 3) Language was changed to specify that at least 30% of all subjects would be from each gender; that half of all subjects would be from the EU, US, or Canada; and that efforts would be made to include subjects from all races. 4) Clarification that the follow-up period would be 5 years from the last dose of study drug (instead of 5 years from the first dose of study drug). 5) Descriptions of informed consent and assent were simplified in anticipation of differences in local (country-specific) rules/regulations. Specifically, statements that assent would be for children older than 12 years were removed. 6) Information on study drug dosing was updated, including addition of language to state that dosing for telaprevir would be based on the subject’s baseline weight, and that the dose for Peg-IFN and RBV would be adjusted using the subject’s current weight at Week 24, if necessary. 7) Ferritin and serology tests for hepatitis C virus and hepatitis A virus were added to the list of assessments to be performed at screening and positive result for anti-hepatitis A virus immunoglobulin M antibody was made an exclusion. 8) Information on detection of liver disease at baseline was updated. It was clarified that results from recent (within 24 months of screening) liver biopsies, if available, would be collected. 9) An exclusion criterion was added for any disease of iron overload, including hemochromatosis, and diseases requiring repeat transfusions. 10) Clarification that a urine home pregnancy test kit would be provided when there were no scheduled study visits.

1) Body weight less than 15 kg was made an exclusion criterion for both Part A and Part B of the study. 2) Exclusions for screening laboratory values were modified to be consistent with regulatory requirements. Exclusions related to thyroid dysfunction were modified. A new exclusion criterion was added for subjects who were pregnant, breastfeeding, or planning to get pregnant during study drug administration or within 6 months after the last dose of RBV. 3) “History of intercurrent illness (e.g., upper respiratory illness with fever) within 5 days prior to the first dose of study drug” was made an exclusion criterion. 4) The exclusion criterion with respect to participation in other studies of investigational drugs was significantly modified, including types of studies, time of previous blood draws, and use of a protease inhibitor. 5) Clarification that subjects in Part B could be with or without cirrhosis. 6) The exclusion criterion on previous treatment experience was clarified to state that subjects in Part A could not have been previously treated with any approved or experimental treatment for hepatitis C. 7) The PK blood sample at 12 hours postdose was deleted. 8) The section on contraception was updated for consistency with regulatory guidance and for clarity. 9) Clarification that telaprevir and RBV were to be taken with food within 30 minutes after eating a meal or snack that was not low fat. 10) The recommendation that the chewable tablets could be crushed and taken with whole milk was removed due to new food testing results. 11) Clarification that investigators were to evaluate subjects’ HCV RNA results by Week 24 and inform subject parents/guardians of their total treatment duration. 12) Clarification of scheduling of follow-up visits and assessments to be performed at these visits and futility rules. 14) Canada was removed in the description of the study population because no sites were planned for this country.

1) The allowance for an overnight visit the night before Day 7 was removed. 2) A mandatory second visit during the screening period was added for laboratory draws (HCV genotype/subtype, HCV serology, human immunodeficiency virus serology, hepatitis A virus serology, hepatitis B virus serology and DNA and antinuclear antibody) for children in the 3- to 6-year-old and 7- to 12-year-old age groups. This was implemented to ensure that the maximum allowable blood volume drawn was not exceeded. 3) References to the use of a breath alcohol test were removed from the document and replaced with a urine alcohol test. The drug and alcohol tests planned for the treatment period were deleted. 4) The time points for ophthalmologic examinations planned for the treatment/follow-up periods were changed to align with the recommendations in the package insert for Peg-IFN. 5) Exclusion criteria for low hemoglobin and for ophthalmologic disorders were clarified and made more specific.