A Phase I-Ib/II Study to Determine the Maximum Tolerated Dose (MTD) of AUY922 Alone and in Combination With Bortezomib, With or Without Dexamethasone, in Patients With Relapsed or Refractory Multiple Myeloma.

Inclusion criteria: * Patients must have a diagnosis of active multiple myeloma. * Phase I and Phase II part: Patients must have received at least 2 but not more than 4 prior line of therapy and their disease has progressed during or after last therapy. * Phase Ib part: Patients must have received no more than 2 prior lines of therapy (excluding dexamethasone as single agent). * ECOG Performance Status of ≤ 2. * Patients must have acceptable neutrophil and platelet counts as well as adequate kidney and liver function. * Patients must have magnesium levels above lower limit of normal or correctable with supplements. * Patients must be willing and able to undergo bone marrow biopsy/aspirate. * Able to sign informed consent. Exclusion criteria: * Prior treatment with any HSP90 or HDAC inhibitor for the treatment of multiple myeloma. * Patients with unresolved diarrhea ≥ CTCAE grade 2. * Patients with acute or chronic liver disease. * Patients using medications that have a relative risk of prolonging the QT interval. * Clinically significant cardiac diseases. * Patients with known disorders due to a deficiency in bilirubin glucuronidation (e.g. Gilbert's syndrome). * Pregnant or lactating women. * Fertile women of childbearing potential (WCBP) not using adequate contraception. * Male patients whose partners are WCBP, not using adequate contraception. * Patients who unwilling or unable to comply with the protocol. * Phase Ib part: Peripheral neuropathy ≥ CTCAE grade 1. * Phase Ib part: Prior treatment with bortezomib. Other protocol-defined inclusion/exclusion criteria may apply