The goal of this clinical trial is to evaluate the safety of TOS-358 in adults with select solid tumors who meet study enrollment criteria. The main questions it aims to answer are:

1. what is the maximum tolerated dose and recommended dose for phase 2?
2. how safe and tolerable is TOS-358 at different dose levels when taken orally once or twice per day?

RBS2418 (investigational product) is a specific immune modulator, working through ectonucleotide pyrophosphatase/phosphodiesterase I (ENPP1), designed to lead to anti-tumor immunity by increasing endogenous 2'-3'-cyclic guanosine monophosphate-adenosine monophosphate (cGAMP) and adenosine triphosphate (ATP levels) and reducing adenosine production in the tumors. RBS2418 has the potential to be an important therapeutic option for subjects both as monotherapy and in combination with other cancer treatments including monotherapy and in combination with other cancer treatments including immunotherapy or chemotherapy. This study is an open-label, multi-site Phase 1a/1b study of RBS2418, a selective ENPP1 inhibitor, in combination with pembrolizumab or other approved anticancer therapies or as a monotherapy in subjects with advanced unresectable, recurrent or metastatic tumors. The phase 1a (dose escalation phase) has been completed. The Phase 1b expansion phase of the study has been increased in size and scope.

This is an umbrella study evaluating the efficacy and safety of multiple treatment combinations in participants with metastatic or inoperable locally advanced breast cancer.

The study will be performed in two stages. During Stage 1, six cohorts will be enrolled in parallel in this study:

Cohort 1 will consist of programmed death-ligand 1 (PD-L1)-positive participants who have received no prior systemic therapy for metastatic or inoperable locally advanced triple-negative breast cancer (TNBC) (first-line \[1L\] PD-L1+ cohort).

Cohort 2 will consist of participants who had disease progression during or following 1L treatment with chemotherapy for metastatic or inoperable locally-advanced TNBC and have not received cancer immunotherapy (CIT) (second-line \[2L\] CIT-nave cohort).

Cohort 3, 5, and 6 will consist of participants with locally advanced or metastatic hormone receptor-positive (HR+), human epidermal growth factor receptor 2 (HER2)-negative disease with one or more PIK3CA mutations.

Cohort 4 will consist of participants with locally advanced or metastatic HER2+ /HER2-low disease with one or more PIK3CA mutations who had disease progression on standard-of-care therapies (HER2+ /HER2-low cohort).

In each cohort, eligible participants will initially be assigned to one of several treatment arms (Stage 1). During Stage 2, participants in the 2L CIT-nave cohort who experience disease progression, loss of clinical benefit, or unacceptable toxicity during Stage 1 may be eligible to continue treatment with a different treatment combination, provided Stage 2 is open for enrollment and all eligibility criteria are met.

This phase Ib trial tests the safety and tolerability of ZEN003694 in combination with an immunotherapy drug called pembrolizumab and the usual chemotherapy approach with nab-paclitaxel for the treatment of patients with triple negative-negative breast cancer that has spread to other parts of the body (advanced). Paclitaxel is in a class of medications called antimicrotubule agents. It stops cancer cells from growing and dividing and may kill them. Nab-paclitaxel is an albumin-stabilized nanoparticle formulation of paclitaxel which may have fewer side effects and work better than other forms of paclitaxel. Immunotherapy with monoclonal antibodies, such as pembrolizumab may help the body's immune system attach the cancer and may interfere with the ability of tumor cells to grow and spread. ZEN003694 is an inhibitor of a family of proteins called the bromodomain and extra-terminal (BET). It may prevent the growth of tumor cells that over produce BET protein. Combination therapy with ZEN003694 pembrolizumab immunotherapy and nab-paclitaxel chemotherapy may help shrink or stabilize cancer for longer than chemotherapy alone.

This phase I trial tests the safety and effectiveness of indium In 111 panitumumab (111In-panitumumab) for identifying the first lymph nodes to which cancer has spread from the primary tumor (sentinel lymph nodes) in patients with head and neck squamous cell carcinoma (HNSCC) undergoing surgery. The most important factor for survival for many cancer types is the presence of cancer that has spread to the lymph nodes (metastasis). Lymph node metastases in patients with head and neck cancer reduce the 5-year survival by half. Sometimes, the disease is too small to be found on clinical and imaging exams before surgery. 111In-panitumumab is in a class of medications called radioimmunoconjugates. It is composed of a radioactive substance (indium In 111) linked to a monoclonal antibody (panitumumab). Panitumumab binds to EGFR receptors, a receptor that is over-expressed on the surface of many tumor cells and plays a role in tumor cell growth. Once 111In-panitumumab binds to tumor cells, it is able to be seen using an imaging technique called single photon emission computed tomography/computed tomography (SPECT/CT). SPECT/CT can be used to make detailed pictures of the inside of the body and to visualize areas where the radioactive drug has been taken up by the cells. Using 111In-panitumumab with SPECT/CT imaging may improve identification of sentinel lymph nodes in patients with head and neck squamous cell cancer undergoing surgery.