Patient description: The patient is a 15-year-old boy with asthma diagnosed a year ago. He presents with shortness of breath, chest tightening and cough. According to his mother, he didn't respond to the usual corticosteroid inhaler. He was admitted to the emergency department with diagnosis of severe asthma exacerbation. He is a candidate for general corticosteroid therapy. Spirometry revealed a forced expiratory volume in the first second (FEV1) of 60% of the predicted. His past medical history is non-significant. His family history is significant for asthma in his mother and his uncle. He used to be treated with combination of inhaled corticosteroids and Zafirlukast.

Clinical trial eligibility criteria: eligible ages (years): 18.0-999.0,  Ovarian Cancer Participants must have histologically confirmed epithelial ovarian, fallopian tube, or primary peritoneal cancer Participants must have completed at least first-line platinum based chemotherapy and surgery with a response, in the opinion of the investigator, defined as no evidence of disease progression or rising CA-125 at any time during front-line treatment Participants must meet for tumor marker-only relapse, defined as CA-125 more than twice the upper limit of normal (35 U/mL) in the setting of a normal baseline CA-125 levels or CA-125 greater than twice the nadir count on two successive measurements for CA-125 values that remain above baseline without measurable radiographic disease Minimum age ≥ 18 years. Because no dosing or adverse event data are currently available on the use of zafirlukast in participants under 18 years of age with ovarian cancer, children are excluded from this study but will be eligible for future pediatric trials Life expectancy of greater than 4 months ECOG performance status ≤ 2 (Karnofsky ≥ 60%, see Appendix A) Participants must be able to swallow tablets Participants must have adequate organ and marrow function as defined below Absolute neutrophil count ≥1,000/mcL Platelets ≥100,000/mcL  Non-epithelial tumors (pure sarcomas) or ovarian tumors with low malignant potential (ie borderline tumors) or mucinous tumors. Mixed mullerian tumors or carcinosarcomas are allowed Participants who have had cytotoxic chemotherapy including bevacizumab or radiotherapy within 4 weeks prior to entering the study. This does not maintenance therapy (>8 weeks prior to enrollment of stable dose) with a PARP inhibitor, such as olaparib or niraparib. (PARP inhibitor, rucaparib is not allowed to be co-administered with CYP2C9 substrates as maintenance therapy as it could increase exposure to zafirlukast) Participants who have ongoing adverse effects from prior anti-cancer therapy greater than National Cancer Institute (NCI) Common Terminology for Adverse Events (CTCAE, v5.0) Grade 1, with the exception of Grade 2 non-hematologic toxicity such as alopecia and peripheral neuropathy Participants who are receiving any other investigational agents Participants with known brain metastases should be excluded from this clinical trial because of their poor prognosis and because they often develop progressive neurologic dysfunction that would confound the evaluation of neurologic and other adverse events History of allergic reactions attributed to compounds of similar chemical or biologic composition to zafirlukast Currently receiving anticoagulant therapy Current daily use of aspirin (> 81 mg daily), clopidogrel (Plavix), cilostazol (Pletal), aspirin-dipyridamole (Aggrenox) (within 10 days) or considered to use regular use of higher doses of non-steroidal anti-inflammatory agents as determined by the treating physician (e.g. ibuprofen > 800 mg daily or equivalent) Participants receiving any medications or substances that are inhibitors or inducers of CYP2C9 are ineligible. 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 participant 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 participant is considering a new over-the-counter medicine or herbal product Participants with uncontrolled intercurrent illness