A Study of ASP3082 in Adults With Advanced Solid Tumors

This is an open-label study. This means that people in this study and clinic staff will know that people will receive ASP3082. The study aims to check how safe and well-tolerated ASP3082 is for people with advanced solid tumors that have a specific mutation called KRAS G12D. This study will be in 2 parts. In Part 1, different small groups of people will receive lower to higher doses of ASP3082 by itself, or together with cetuximab. Any medical problems will be recorded at each dose. This is done to find suitable doses of ASP3082, by itself or together with cetuximab, to use in Part 2 of the study. The first group will receive the lowest dose of ASP3082. A medical expert panel will check the results from this group and decide if the next group can receive a higher dose of ASP3082. The panel will do this for each group until all groups have received ASP3082 (by itself or together with cetuximab) or until suitable doses have been selected for Part 2. In Part 2, ASP3082 will be given in by itself, or in combination with the other study treatments. Study treatments will be given through a vein. This is called an infusion. Each treatment cycle is 21 or 28 days long. They will continue treatment until: they have medical problems from the treatment they can't tolerate; their cancer gets worse; they start other cancer treatment; or they ask to stop treatment.

Inclusion Criteria: * Participant has locally advanced (unresectable) or metastatic solid tumor malignancy with documented Kirsten rat sarcoma viral oncogene homolog \[KRAS\] G12D mutation and has received prior standard therapy and the investigator does not see any further clinical benefit from continuing such targeted therapy, or is ineligible to receive standard approved therapies (no limit to the number of prior treatment regimens). * For the ASP3082 monotherapy escalation cohorts, participants with solid tumor malignancies are allowed to be enrolled. Participants with other known KRAS G12 mutations will not be eligible for the study * For ASP3082 combination therapy with Nab-P+GEM or FOLFIRINOX or NALRIFOX: Participant must have mPDAC that has not been previously treated with chemotherapy. If a participant received (neo)adjuvant therapy, tumor recurrence or disease progression must have occurred at least 6 months after completing the last dose of the (neo)adjuvant therapy. * Participant consents to provide tumor specimen in a tissue block or unstained serial slides or a tumor biopsy (core needle biopsy or excision) obtained after the last interventional treatment, but prior to start of study intervention. Participant also consents to provide a sample for tumor biopsy during the treatment period as indicated in the study protocol. If a participant cannot provide a fresh tissue biopsy sample, the site should consult with the sponsor/study medical monitor. * Participant has at least 1 measurable lesion per Response Evaluation Criteria in Solid Tumors (RECIST) v1.1. Lesions situated in a previously irradiated area are considered measurable if progression has been demonstrated in such lesions. * Participant has an ECOG performance status of 0, 1 or 2 for dose escalation, and 0 or 1 for dose expansion. * Participant's last dose of prior antineoplastic therapy, including any immunotherapy, was 21 days or 5 half-lives, whichever is shorter, prior to initiation of study intervention administration. * Participant has completed any radiotherapy (including stereotactic radiosurgery) at least 14 days prior to the start of study intervention administration. Participants must have recovered from all radiation-related toxicities, not require corticosteroids (NOTE: Physiologic replacement dose of hydrocortisone or its equivalent \[defined as up to 30 mg per day of hydrocortisone, 2 mg per day of dexamethasone, or up to 10 mg per day of prednisone\] is permitted), and not have active radiation pneumonitis. A 1-week washout is permitted for palliative radiation (\ 450 milliseconds (msec) (men) or \>470 msec (women) during screening. * Participant has received prior treatment with a specific KRAS G12D inhibitor/degrader or pan-RAS inhibitor/degrader targeting KRAS G12D. Participants who received prior treatment with a KRAS G12D inhibitor/degrader are eligible for the ASP3082 combination therapy cohort. * Participant has an active infection requiring intravenous antibiotics within 14 days prior to study intervention. * Participant is expected to require another form of antineoplastic therapy while on study treatment. * Participant has any condition which makes the participant unsuitable for study participation (such as psychiatric illness/social situations that would limit compliance with study requirements). * Participant has had major surgery within 4 weeks prior to first dose of study intervention. For ASP3082 Combination Therapy: * Prior discontinuation of cetuximab treatment due to toxicity or intolerance of cetuximab. * History of interstitial lung disease requiring systemic steroid treatment. Note that a participant with resolved pulmonary infections or radiation pneumonitis is eligible.