• HCC part only:

• Participants with confirmed diagnosis of unresectable HCC with any of the following criteria:

‣ Histologically or cytologically confirmed diagnosis of HCC, excluding fibrolamellar, sarcomatoid or mixed cholangio-HCC tumors

‣ Clinically confirmed diagnosis of HCC according to American Association for the Study of Liver Diseases (AASLD) criteria, including cirrhosis of any etiology and/or chronic hepatitis B or C infection

• ST part only (except for HCC):

• Participants with histologically or cytologically confirmed diagnosis of solid tumor for which no alternative standard therapy or no effective therapy exists

• Life expectancy of \>=12 weeks

• Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 to 1

• All AEs due to previous anti-cancer therapy have either returned to Grade 0 to 1 except for alopecia or up to Grade 2 peripheral neuropathy (renal/bone marrow/liver function should meet the inclusion criteria)

• Adequate washout period before study drug administration:

∙ Chemotherapy and radiotherapy: 3 weeks or 5 times the half-life, whichever is shorter

‣ Any antitumor therapy with antibody: 4 weeks or more

‣ Any investigational drug or device: 4 weeks or more

‣ Blood/platelet transfusion or granulocyte colony-stimulating factor (G-CSF): 2 weeks or more Note: Participants must have recovered from all radiation-related toxicities, not require corticosteroids, and not had radiation pneumonitis

• Adequate controlled blood pressure (BP), renal function, bone marrow function, liver function, and serum mineral level

• At least one measurable lesion based on mRECIST (for HCC Subparts in Dose Escalation Part) or on RECIST 1.1 (for Other ST Subparts in Dose Escalation Part and all subparts in Expansion and Dose Optimization Parts) meeting following criteria

‣ At least 1 lesion of \>=1.0 centimeter (cm) in the longest diameter for a non-lymph node or \>=1.5 cm in the short-axis diameter for a lymph node that is serially measurable according to RECIST 1.1 using computerized tomography (CT)/magnetic resonance imaging (MRI)

⁃ Lesions that have had external beam radiotherapy or loco-regional therapies such as radiofrequency ablation, or transarterial chemoembolisation (TACE)/ transarterial embolization (TAE) must show evidence of progressive disease based on RECIST 1.1 to be deemed a target lesion

• For HCC participants only: Child-Pugh score A. Note: If Child-Pugh score 7 or more was observed during Screening or Baseline, the participant is ineligible and re-assessment of the Child-Pugh score is not permitted

• For HCC participants only: Participants categorized to stage B (not amenable to locoregional therapy or refractory to locoregional therapy, and not amenable to a curative treatment), or stage C based on Barcelona Clinic Liver Cancer (BCLC) staging system

⁃ For HCC Subpart in Expansion Part only: prior systemic therapy for locally advanced or metastatic disease is as defined below

⁃ a. Participants who have received only one prior line of immuno oncology (IO) based regimen and have progressed on or after prior treatment with IO based regimen, or IO ineligible participants who have received no prior systemic therapy. Participants who previously received lenvatinib treatment are ineligible

⁃ For CRC Subpart in Expansion Part only: participants must have received at least 2 prior regimens (not exceeding 4 prior regimens) or could not tolerate standard treatment and must have received the following prior therapies in the metastatic setting if approved and locally available (progressed on at least 1 prior regimen in the metastatic setting or could not tolerate standard treatment):

⁃ Note: Adjuvant chemotherapy counts as prior systemic treatment if there is documented disease progression within 6 months of treatment completion Note: If a participant is determined to be intolerant to prior standard treatment, the participant must have received at least of 2 cycles of that therapy Note: Participants who have received oral tyrosine kinase inhibitor (example, regorafenib) are ineligible

∙ Fluoropyrimidine, irinotecan and oxaliplatin with or without an anti-Vascular endothelial growth factor (VEGF) monoclonal antibody (mAb) (example, bevacizumab) Note: Capecitabine is acceptable as equivalent to fluoropyrimidine in prior treatment Note: Participants who have previously received fluoropyrimidine, oxaliplatin, and irinotecan as part of the same and only chemotherapy regimen, example, FOLFOXIRI or FOLFIRINOX, may be eligible after discussion with the Sponsor

∙ Chemotherapy with anti- epidermal growth factor receptor (EGFR) mAb (cetuximab or panitumumab) for participants with rat sarcoma virus (RAS) (Kirsten rat sarcoma viral oncogene homolog \[KRAS)/ NRAS\]) wild type (WT) CRC Note: RAS (KRAS/NRAS) WT participants with right or left CRC lesions who may have not been treated with anti-EGFR mAb based on local guidelines are eligible

∙ BRAF inhibitor (in combination with cetuximab ± binimetinib) for BRAF V600E mutated tumors

∙ Immune checkpoint inhibitor for participants with microsatellite instability-high (MSI-H) CRC

⁃ For EC Subpart in Expansion Part only: Participants must have EC that has progressed after prior platinum-based chemotherapy and an anti-programmed cell death (ligand) 1 (PD-\[L\])1)-directed therapy for EC (participants ineligible for IO therapy who have progressed after prior platinum-based chemotherapy are eligible). Up to 3 prior systemic therapies, of which up to 2 for metastatic or locally advanced disease, are permitted Note: There is no restriction regarding prior hormonal therapies For Dose Optimization Part only: Participants must have EC that has progressed after prior platinum-based chemotherapy and an anti-PD-(L)1-directed therapy for EC. Up to 3 lines of prior therapy, regardless of setting, are allowed. Participants must be eligible for treatment with either single-agent paclitaxel or single-agent doxorubicin as determined by the investigator, with consideration of previous therapies received for EC. Note: Prior hormonal therapy and radiation are allowed and do not count as prior lines of therapy.