Testing the Addition of an Anti-cancer Drug, Elimusertib (BAY 1895344) ATR Inhibitor, to the Chemotherapy Treatment (Gemcitabine) for Advanced Pancreatic and Ovarian Cancer, and Advanced Solid Tumors (NCT04616534)

Usually NOT eligible if any of the following apply:

• Exclusion Criteria:
• Patients cannot receive chemotherapy, targeted therapy or immunotherapy within 3 weeks of study entry
• Patients who have had radiotherapy within 4 weeks prior to entering the study
• Patients who have not recovered from adverse events due to prior anti-cancer therapy (i.e., have residual toxicities \> grade 1) with the exception of alopecia and lymphopenia
• Participants must not have received investigational therapy administered =\< 4 weeks or within a time interval less than at least five half-lives of the investigational agent, whichever is longer, before initiation of protocol therapy
• Participants with known untreated brain metastases are excluded from this clinical trial
• History of allergic reactions attributed to compounds of similar chemical or biologic composition to elimusertib (BAY 1895344) or gemcitabine
• Patients receiving any medications that are substrates of CYP3A4 with a narrow therapeutic window, or strong inhibitors/inducers of CYP3A4 are ineligible, if they cannot be transferred to alternative medication. Because the lists of these agents are constantly changing, it is important to regularly consult a frequently-updated medical reference. As part of the enrollment/informed consent procedures, the patient will be counseled on the risk of interactions with other agents, and what to do if new medications need to be prescribed or if the patient is considering a new over-the-counter medicine or herbal product
• Patients with uncontrolled intercurrent illness including but not limited to ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, clinically significant cardiac arrhythmia, uncontrolled major seizure disorder, unstable spinal cord compression, superior vena cava syndrome or psychiatric illness/social situations that would limit compliance with study requirements are excluded
• Patients with psychiatric illness/social situations that would limit compliance with study requirements
• Pregnant women are excluded from this study because elimusertib (BAY 1895344) as a DNA-damage response inhibitor, and gemcitabine may have the potential for teratogenic or abortifacient effects. Because there is an unknown but potential risk for adverse events in nursing infants secondary to treatment of the mother with elimusertib (BAY 1895344) breastfeeding should be discontinued if the mother is treated with elimusertib (BAY 1895344) and for 4 months after end of treatment. These potential risks may also apply to other agents used in this study
• Patients who have successfully undergone treatment for another, unrelated clinically relevant cancer, \>= 3 years post final treatment, are eligible to participate in this study