A Study to Evaluate the Potential Benefit of the Addition of BYL719 to Paclitaxel in the Treatment of Breast Cancer and Head-and-neck Cancer

Inclusion criteria For entire trial: 1. \- Adult \> or = 18 years old 2. \- has signed the Informed Consent Form (ICF) 3. \- has at least one measurable or non-measurable disease as per RECIST 1.1 4. \- has tumor tissue available for the analysis as described in the protocol 5. \- has adequate bone marrow and organ function as defined in the protocol 6. \- is able to swallow and retain oral medication for the dose escalation part, ALL above PLUS 7. \- has a histologically-confirmed, advanced unresectable solid tumors who have progressed on standard therapy (or not been able to tolerate) within three months before screening/baseline visit or for whom no standard anticancer therapy exists. 8. \- has an Eastern Cooperative Oncology Group (ECOG) performance status ≤2 For dose expansion part, patient has ALL of above first six criteria PLUS either: 9- has a histologically/cytologically-confirmed HNSCC as detailed in the protocol and an ECOG performance status ≤ 1 or: * Patient is a Female with a histologically and/or cytologically confirmed diagnosis of breast cancer as detailed in the protocol and an ECOG performance status ≤ 1 Common exclusion criteria to Dose escalation and Dose expansion parts: 1. \- has received previous treatment with a PI3K or AKT inhibitor as described in the protocol 2. \- has a known hypersensitivity to paclitaxel or other products containing Cremophor 3. \- has a contraindication to use the standard pre-treatment for paclitaxel 4. \- has a primary central nervous system (CNS) tumor or CNS tumor involvement as detailed in the protocol 5. \- has not recovered to grade 1 or better (except alopecia) from related side effects of any prior antineoplastic therapy 6. \- has received radiotherapy \> or = 4 weeks prior to starting study drugs, with exception of palliative radiotherapy, who has not recovered from side effects of such therapy to baseline or Grade ≤ 1 and/or from whom ≥ 30% of the bone marrow was irradiated 7. \- has peripheral sensory neuropathy with functional impairment (CTC grade 2 neuropathy or higher) 8. \- has undergone major surgery ≤ 4 weeks prior to starting study treatment or who has not recovered from side effects of such procedure 9. \- has a clinically significant cardiac disease or impaired cardiac function as detailed in the protocol 10. \- is currently receiving medication with a known risk of prolonging the QT interval or inducing Torsades de Pointes (TdP) and the treatment cannot either be discontinued or switched to a different medication prior to starting study drug treatment 11. \- has diabetes mellitus requiring insulin treatment and/or with clinical signs 12. \- has impaired gastrointestinal (GI) function or GI disease as described in the protocol 13. \- has a known positive serology for human immunodeficiency virus (HIV), active Hepatitis B, and/or active Hepatitis C infection 14. \- has any other condition that would, in the Investigator's judgment, preclude patient's participation in the clinical study due to safety concerns or compliance with clinical study procedures 15. \- is currently receiving treatment with drugs known to be moderate or strong inhibitors or inducers of isoenzymes CYP3A or CYP2C8 as detailed in the protocol 16. \- is currently receiving treatment with agents that are metabolized solely by CYP3A and/or have a narrow therapeutic window 17. \- has a history of another malignancy within 2 years prior to starting study treatment, except cured basal cell carcinoma of the skin or excised carcinoma in situ of the cervix 18. \- Patient has a history of non-compliance to medical regimen or inability to grant consent 19. \- Pregnant or nursing (lactating) women 20. \- does not apply highly effective contraception during the study and through the duration as defined in the protocol For the HNSCC patient's cohort additional exclusion criteria are: 21- Treatment with more than one prior chemotherapy for recurrent/metastatic disease as detailed in the protocol 22- Prior taxane treatment for metastatic disease additional exclusion criteria for breast cancer patients' cohort: \- has received any prior cytotoxic therapy for the inoperable locally advanced (recurrent or progressive) or metastatic disease, or who had a progression/recurrent disease within 6 months after completion of an adjuvant/neoadjuvant therapy as described in the protocol Other protocol-defined inclusion/exclusion criteria may apply