Search

Panobinostat is a potent pan-deacetylase inhibitor that affects the growth and survival of multiple myeloma (MM) cells through alteration of epigenetic mechanisms and protein metabolism. Panobinostat plus bortezomib and dexamethasone (PAN-BTZ-Dex) led to a significant increase in progression-free survival (PFS) vs placebo plus bortezomib and dexamethasone (Pbo-BTZ-Dex) in patients with relapsed or relapsed and refractory MM in the phase 3 PANORAMA 1 trial. This subgroup analysis evaluated outcomes in patients in the PANORAMA 1 trial based on prior treatment: a prior immunomodulatory drug (IMiD; n = 485), prior bortezomib plus an IMiD (n = 193), and ≥2 prior regimens including bortezomib and an IMiD (n = 147). Median PFS with PAN-BTZ-Dex vs Pbo-BTZ-Dex across subgroups was as follows: prior IMiD (12.3 vs 7.4 months; hazard ratio [HR], 0.54; 95% confidence interval [CI], 0.43-0.68), prior bortezomib plus IMiD (10.6 vs 5.8 months; HR, 0.52; 95% CI, 0.36-0.76), and ≥2 prior regimens including bortezomib and an IMiD (12.5 vs 4.7 months; HR, 0.47; 95% CI, 0.31-0.72). Common grade 3/4 adverse events and laboratory abnormalities in patients who received PAN-BTZ-Dex across the prior treatment groups included thrombocytopenia, lymphopenia, neutropenia, diarrhea, and asthenia/fatigue. Incidence of on-treatment deaths among patients who received prior bortezomib and an IMiD (regardless of number of prior regimens) was similar between treatment arms. This analysis demonstrated a clear PFS benefit of 7.8 months with PAN-BTZ-Dex among patients who received ≥2 prior regimens including bortezomib and an IMiD, a population with limited treatment options and poorer prognosis. This trial was registered at www.clinicaltrials.gov as #NCT01023308., (© 2016 by The American Society of Hematology.)

Although it has been shown that unfractionated bone marrow, hematopoietic stem cells, common myeloid progenitors, and bipotent megakaryocyteerythrocyte progenitors can give rise to megakaryocyte colonies in culture, monopotent megakaryocyte-committed progenitors (MKP) have never been prospectively isolated from the bone marrow of adult mice. Here, we use a monoclonal antibody to the megakaryocyte-associated surface protein, CD9, to purify MKPs from the c-kit(+)Sca-1(-)IL7Ralpha(-)Thy1.1(-)Lin(-) fraction of adult C57BLKa-Thy1.1 bone marrow. The CD9(+) fraction contained a subset of CD41(+)FcgammaR(lo)CD34(+)CD38(+) cells that represent approximately 0.01% of the total nucleated bone marrow cells. They give rise mainly to colony-forming unit-megakaryocytes and occasionally burst-forming unit-megakaryocytes, with a plating efficiency >60% at the single-cell level. In vivo, MKPs do not have spleen colony-forming activity nor do they contribute to long-term multilineage hematopoiesis; they give rise only to platelets for approximately 3 weeks. Common myeloid progenitors and megakaryocyteerythrocyte progenitors can differentiate into MKPs after 72 h in stromal cultures, indicating that MKPs are downstream of these two progenitors. These isolatable MKPs will be very useful for further studies of megakaryopoiesis as well as the elucidation of their gene expression patterns.