Clinical perspectives on treatment of rifampicin-resistant/multidrug-resistant TB.

Rapid diagnostics, newer drugs, repurposed medications, and shorter regimens have radically altered the landscape for treating rifampicin-resistant TB (RR-TB) and multidrug-resistant TB (MDR-TB). There are multiple ongoing clinical trials aiming to build a robust evidence base to guide RR/MDR-TB treatment, and both observational studies and programmatic data have contributed to advancing the treatment field. In December 2019, the WHO issued their second 'Rapid Communication´ related to RR-TB management. This reiterated their prior recommendation that a majority of people with RR/MDR-TB receive all-oral treatment regimens, and now allow for specific shorter duration regimens to be used programmatically as well. Many TB programs need clinical advice as they seek to roll out such regimens in their specific setting. In this Perspective, we highlight our early experiences and lessons learned from working with National TB Programs, adult and pediatric clinicians and civil society, in optimizing treatment of RR/MDR-TB, using shorter, highly-effective, oral regimens for the majority of people with RR/MDR-TB.

Human leukaemic stem cells: a novel target of therapy.

Acute myeloid leukaemia (AML) is a life-threatening haematopoietic disease that is characterized by clonal growth and the accumulation of myelopoietic progenitor cells. Although AML cells only have a limited potential to undergo differentiation and maturation, each AML clone is organized in a hierarchical manner similar to normal haematopoiesis. Recent data have shown that each AML clone consists of leukaemic stem cells and their progeny, and that AML stem cells differ from more mature cells in several aspects, including survival and target antigen profiles. Most importantly, AML stem cells, but not their progeny, have the capacity to repopulate haematopoietic tissues with leukaemias in NOD/SCID mice. Furthermore, AML stem cells are thought to be responsible for the infinite growth of leukaemias in patients with AML. The phenotypic properties of AML stem cells have also been described. In most cases, these cells are detectable within the CD34+, CD38-, Lin-, CD123+ subpopulation of AML cells. Because of their AML-initiating and -renewing capacity and their unique phenotype, which includes several molecular targets of drug therapy, AML stem cells have recently been proposed as novel important target cell populations in the context of curative therapies. The present article gives an overview of our knowledge about AML stem cells, their phenotype, and their role as a 'therapy-target' in new concepts to treat and to cure patients with AML.

High spontaneous colony growth in chronic myelomonocytic leukemia correlates with increased disease activity and is a novel prognostic factor for predicting short survival.

We have originally shown that spontaneous granulocyte/macrophage colony (CFU-GM) formation in semisolid medium is a characteristic in vitro feature of chronic myelomonocytic leukemia (CMML). However, the clinical significance of spontaneous CFU-GM growth in CMML is unknown so far. CFU-GM growth characteristics were studied in semisolid cultures in the absence of exogenous cytokines using peripheral blood mononuclear cells in 30 patients with CMML at first presentation. The median number of CFU-GM/10(5) MNC of all patients was 48.5 (range 0-622) with 18 patients having colony numbers below 100 (low CFU-GM growth) and 12 patients above 100 (high CFU-GM growth). Kaplan-Meier analysis revealed that patients with high CFU-GM growth had a significantly shorter survival than patients with low CFU-GM growth (median 6.5 vs. 44.5 months, p<0.00002). The probability of survival after 2 years was 60.5% for patients with low colony growth but 0% in those with high colony formation. Patients with CFU-GM >100 had a significantly higher WBC count, a higher LDH, and a higher number of blast cells in blood and bone marrow than patients with low colony growth. Moreover, patients with high colony growth had more often splenomegaly and lower platelet counts. In seven patients, in whom semisolid in vitro cultures were performed after transformation into RAEBT/AML, spontaneous colony growth was significantly increased as compared to CFU-GM growth in patients before transformation (median number/10(5) MNC 533, range 212-4553, p<0.005). This study demonstrates that high (>100) spontaneous CFU-GM formation in CMML at presentation correlates with increased disease activity and represents a novel and important prognostic factor predicting for short survival of CMML patients.

Numbers of colony-forming progenitors in patients with systemic mastocytosis: potential diagnostic implications and comparison with myeloproliferative disorders.

BACKGROUND: An increase in colony-forming progenitor cells (CFU) is typically seen in myeloproliferative disorders (MPD). Systemic mastocytosis (SM) is a haemopoietic neoplasm involving myeloid progenitors similar to MPD. In the present study, we measured the levels of peripheral blood (pb) and bone marrow (bm) CFU in patients with different categories of SM, and compared them with those obtained in MPD patients and healthy controls. MATERIALS AND METHODS: Numbers of CFU (CFU-GM, BFU-E, CFU-GEMM) were measured in a colony assay in 25 patients with SM [indolent SM (ISM), n = 15; smouldering SM (SSM), n = 3; SM with an associated haematologic clonal non-mast cell lineage disease (SM-AHNMD), n = 5; aggressive SM (ASM), n = 1; mast cell leukaemia (MCL), n = 1] and 37 with MPD [chronic myeloid leukaemia (CML), n = 10; polycythemia vera (PV), n = 8; essential thrombocytosis (ET), n = 9; idiopathic myelofibrosis (IMF), n = 10]. RESULTS: In the patients with MPD, elevated numbers of pb CFU were detected in all groups when compared with healthy controls (P < 0.05). In most of the patients with ISM, circulating CFU levels (CFU-GM, BFU-E, and CFU-GEMM) were within the normal range. In SSM, pb CFU-GM levels were normal in two patients, and elevated in a third patient. In the "SM-AHNMD-group", CFU levels were found to reflect the nature of the AHNMD: in SM with concomitant acute myeloid leukaemia (SM-AML, n = 2), the levels of CFU were low or undetectable, whereas in SM with chronic myelomonocytic leukaemia (SM-CMML, n = 2), elevated numbers of pb CFU-GM were found. CONCLUSION: The numbers of CFU are normal in patients with ISM, but elevated in some patients with SSM and SM-CMML. An elevated CFU level in SM should raise the suspicion of an associated MPD (CMML) or smouldering SM, a novel SM-subtype that shares several features with MPD and sometimes progresses to an overt SM-MPD.

Circulating myeloid colony-forming cells predict survival in myelodysplastic syndromes.

The growth characteristics and the prognostic value of cytokine-stimulated myeloid colony formation from peripheral blood mononuclear cells (PBMC) of patients with myelodysplastic syndromes (MDS) are largely unknown. In this study we have determined the number of myeloid colony-forming units (mCFUs) in semisolid medium from 112 MDS patients and correlated them with French-American-British (FAB) type, the international prognostic scoring system (IPSS), karyotype, peripheral blood (PB) and bone marrow (BM) blast cells, cytopenias, lactate dehydrogenase (LDH), and survival data. Concerning the FAB classification, lower median mCFUs were found in patients with refractory anemia (RA) and refractory anemia with ringed sideroblasts (RARS) compared to refractory anemia with excess of blast cells (RAEB) and refractory anemia with excess of blasts cells in transformation (RAEB-T). In vitro growth in MDS clearly correlated with the cytogenetic risk groups defined by the IPSS (30.5/10(5) PBMCs with favorable karyotypes, 191 in the intermediate prognostic group, 677 with unfavorable cytogenetics, p=0.015 favorable vs unfavorable). BM blast cells >5% (60.5 vs 255 colonies, p=0.032) as well as LDH levels above the normal limit (64.5 vs 425 colonies, p=0.045) were also associated with higher colony formation. Patients were stratified according to the number of circulating mCFUs into a low growth, intermediate growth and high growth group. Median survival was 343 days in the high growth, 1119 days in the low growth, and 2341 days in the intermediate growth group ( p=0.0002). Multivariate analyses revealed colony growth ( p=0.0056), PB blast cells ( p=0.0069), cytogenetic risk group ( p=0.024), and platelet count ( p=0.018) to predict survival in our patients. After inclusion of the IPSS risk categories, mCFU levels remained a highly predictive parameter for survival ( p=0.0056) and acute myeloblastic leukemia (AML) transformation ( p=0.0003).