The purpose of this study is to evaluate the investigational oral drug AMXT 1501 in combination with oral eflornithine (DFMO). An investigational drug is one that has not been approved by the U.S. Food \& Drug Administration (FDA), or any other regulatory authorities around the world for use alone or in combination with any drug, for the condition or illness it is being used to treat.

The goals of this part of the study are:

* Establish a recommended dose of AMXT 1501 in combination with DFMO
* Test the safety and tolerability of AMXT 1501 in combination with DFMO
* To determine the activity of study treatments chosen based on:
* How each subject responds to the study treatment
* How long a subject lives without their disease returning/progressing

This is a phase 3 open-label, randomized, controlled, multicenter study to compare petosemtamab vs investigator's choice monotherapy in HNSCC patients for the second- and third-line treatment of incurable metastatic/recurrent disease.

The purpose of this study is to determine if the radiotracer, \[68Ga\]Ga-ABY-025, used for PET imaging can help us better identify and visualize lesions or tumors, in patients who are receiving standard of care therapy HER2+ cancers.

The goal of this study is to provide access to brexucabtagene autoleucel for patients diagnosed with a disease approved for treatment with brexucabtagene autoleucel, that is otherwise out of specification for commercial release.