This is a study of dalotuzumab given as monotherapy and in combination with ridaforolimus for pediatric participants with advanced solid tumors. This study will have three parts. Part 1 will find a maximum tolerated dose (MTD) and collect pharmacokinetic (PK) data for dalotuzumab alone. Part 2 will find an MTD and collect PK data for dalotuzumab in combination with ridaforolimus. Part 3 will be an expansion cohort at the recommended Phase 2 dose (RPTD) found in Part 2 to confirm the RPTD and look at the potential efficacy of the combination therapy.

Inclusion criteria:

• Participants of age 3 to 17 years for Part 1 of the study and age 6 to 17 years for Parts 2 and 3 of the study
• Histologic or cytologic diagnosis of a malignant solid tumor, including tumors of the central nervous system and lymphoma, that have progressed despite standard therapy or for which no effective standard therapy is known.
• Measurable or non-measurable disease for Parts 1 and 2; measurable disease for Part 3
• Parts 2 and 3: must be able to swallow tablets
• Performance Status: Lansky Play Scale ≥70 for children <10 years of age; Karnofsky score ≥70 for children ≥10 to <16 years; or Eastern Cooperative Oncology Group (ECOG) Status 0-2 for patients age 16 and older
• Adequate organ function
• For females of reproductive potential, a negative pregnancy test must be documented within 72 hours of receiving the first dose of study medication
• Participants of reproductive potential must agree to use (or have their partner use) adequate contraception throughout the study, starting with Visit 1 through 30 days after the last dose of study drug

Exclusion criteria:

• Currently receiving any other investigational agents or using any investigational devices
• Leukemia
• Previously received dalotuzumab or other IGF-1R inhibitors for Part 1
• History of allergic reactions attributed to compounds of similar chemical or biologic composition to dalotuzumab or ridaforolimus
• Persistent acute toxicity from previous therapy ≥Grade 2 (excluding alopecia, neuropathy, or hearing loss)
• Uncontrolled intercurrent illness despite adequate therapy
• Pregnant or breastfeeding
• For Parts 2 and 3: requirement for concurrent treatment with medications that are inducers or inhibitors of cytochrome P450 (CYP3A)
• Poorly controlled Type 1 or 2 diabetes