Dabrafenib–Panobinostat Salt: Improving the Dissolution Rate and Inhibition of BRAF Melanoma Cells

[Image: see text] Cocrystallization of the drug–drug salt-cocrystal of the histone deacetylase inhibitor (HDACi) panobinostat (PAN) and b-rapidly accelerated fibrosarcoma (BRAF) inhibitor dabrafenib (DBF) afforded single crystals of a two-drug salt stabilized by N(+)–H···O and N(+)–H···N(–) hydrogen bonds between the ionized panobinostat ammonium donor and dabrafenib sulfonamide anion acceptor in a 12-member ring motif. A faster dissolution rate for both drugs was achieved through the salt combination compared to the individual drugs in an aqueous acidic medium. The dissolution rate exhibited a peak concentration (C(max)) of approximately 310 mg cm(–2) min(–1) for PAN and 240 mg cm(–2) min(–1) for DBF at a T(max) of less than 20 min under gastric pH 1.2 (0.1 N HCl) compared to the pure drug dissolution values of 10 and 80 mg cm(–2) min(–1), respectively. The novel and fast-dissolving salt DBF(–)·PAN(+) was analyzed in BRAF(V600E) melanoma cells Sk-Mel28. DBF(–)·PAN(+) reduced the dose–response from micromolar to nanomolar concentrations and lowered IC(50) (21.9 ± 7.2 nM) by half compared to PAN alone (45.3 ± 12.0 nM). The enhanced dissolution and lower survival rate of melanoma cells show the potential of novel DBF(–)·PAN(+) salt in clinical evaluation.