A Study of Amivantamab Alone or in Addition to Other Treatment Agents in Participants With Recurrent/Metastatic Head and Neck Cancer

Inclusion Criteria:

• Have histologically or cytologically confirmed recurrent/metastatic head and necksquamous cell carcinoma (R/M HNSCC) that is considered incurable by local therapies.Acceptable prior lines of therapy will be determined according to specific cohort 1, 2, 3A and 3B: (a) The eligible primary tumor locations are the oropharynx, oralcavity, hypopharynx, or larynx; (b) Any known p16 status of tumor must be negative (Note: All participants with an oropharyngeal tumor must have results of p16 status,per local testing); (c) Participants must provide local testing results ofprogrammed cell death ligand 1 (PD-L1) status, if available; Cohort 4: (a) Patientsmust have primary tumor location in oropharynx. Unknown primary tumors are notincluded (b) Primary tumor must be HPV-positive, confirmed by positive p16 test orhigh-risk human papillomavirus (HPV) in-situ hybridization (ISH) in tissue (currentor archival) (c) Participants must provide local testing results of PD-L1 status, ifavailable; Cohort 5 (a) The eligible primary tumor locations are the oropharynx,oral cavity, hypopharynx, or larynx; (b) HPV status must be known (either positiveor negative) for patients with primary tumor location in oropharynx with p16 test orhigh-risk HPV ISH in tissue; (c) Participants must provide local testing results ofPD-L1 status

• Participants in Cohorts 1, 2, 3B, 4 and 5 must have measurable disease according toRECIST version 1.1. Participants in Cohort 3A must have evaluable disease (definedas having at least 1 non-target lesion according to RECIST version 1.1

• Toxicities from previous anticancer therapies should have resolved to baselinelevels or to Grade 1 or less prior to the first dose of study treatment (except foralopecia or post-radiation skin changes [any grade], Grade less than or equal to [<=]2 peripheral neuropathy and Grade <=2 hypothyroidism stable on hormonereplacement)

• Have an Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 1

• Participant must have adequate organ and bone marrow function as follows, withouthistory of red blood cell transfusion, platelet transfusion, or use of granulocytecolony-stimulating factor within 7 days prior to the date of the laboratory test.

Participants should have: a) Hemoglobin >=9 grams per deciliter (g/dL); b) Neutrophils >=1.5 x 10^3/mcg; c) Platelets >=100 x 10^3/mcg

Exclusion Criteria:

• Uncontrolled illness including any medical history or current (non-infectious)interstitial lung disease (ILD)/ pneumonitis/ pulmonary fibrosis, or where suspectedILD/pneumonitis/pulmonary fibrosis cannot be ruled out by imaging at screening

• Participant with untreated brain metastases leptomeningeal disease, or spinal cordcompression not definitively treated with surgery or radiation

• Participant with a history of clinically significant cardiovascular disease

• Received prior chemotherapy, targeted cancer therapy, immunotherapy, or treatmentwith an investigational anticancer agent within 2 weeks or 4 half-lives, whicheveris longer, before the first administration of study treatment. The maximum requiredwashout is 28 days

• Received radiotherapy for palliative purposes within 7 days of the firstadministration of study treatment