A Bioinformatic Approach to the Clinical Evaluation of Linear Commitment Versus Cloud (Continuum of Low Primed UnDifferentiated) Models for Hematopoiesis Using Plinabulin Clinical Trial Data

Introduction

An alternative to the classical Lineage Commitment model for hematopoiesis is the Continuum of Low Primed UnDifferentiated (CLOUD) model (Velten, Nat Cell Biol 2017). Lineage Commitment and CLOUD data are largely derived from in-vitro methods. In-vivo clinical data that is devoid of analytical method-induced 'bias' is sparse. Plinabulin (Plin), is a novel agent that prevented chemotherapy-induced-neutropenia (CIN) in cancer patients (pts) through protection of bone marrow stem cells (Tonra, 2020; Blayney, ASH 2021). Plin, therefore could serve as a pharmacological interventional approach to evaluate Linear Commitment versus CLOUD for hematopoiesis in an in-vivo, human setting. Peripheral blood cell counts (PBCs) from the myeloid, lymphoid, and erythroid lineages in cancer pts receiving myelosuppressive chemotherapy (Chemo) with and without Plin were analyzed using bioinformatics.

Method

PBCs from cancer pts (Breast, NSCLC, HRPC) receiving Chemo (TAC [docetaxel 75 mg/m², doxorubicin 50 mg/m², and cyclophosphamide 500 mg/m²; Study 106; NCT03294577] or docetaxel 75 mg/m² alone; Study 105 NCT03102606), with Plin doses of 5, 10, 20, 30 mg/m² (or equivalent) or placebo (Plac; without plinabulin) were collected at screening, predose (cycle (C) 1 day (D) 1,) and at 24 hours after Chemo with or without Plin (C1D2). Plin was given as a single dose by 30 min IV infusion, 30 mins after (the last) Chemo on D1. All pts (with and without Plin) had received dexamethasone 16 mg per day on D-1, 1, and 2 as premedication for docetaxel (and TAC). Blood draws for absolute counts of PBCs, segmented neutrophil (N), band neutrophil (BAND), monocyte (M), eosinophil (E), basophil (B), lymphocyte (L), erythrocyte (RBC), platelet (P), and immature cells, were analysed by Central Laboratory (Covance). Bioinformatic analysis was performed by FIOS Genomics. To detect treatment-specific effects, exploratory principal component analysis (PCA) and Pearson correlation analysis were performed. 'Limma' linear modelling was used to assess treatment impact on cell counts (C1D1 vs screening; C1D2 vs C1D1) and changes in cell counts (screening to C1D1; C1D1 to C1D2), adjusting for relevant clinical variables. Further correlation and clustering analyses per hematopoietic hierarchy (MEP, GMP, and GLP) were performed to determine correlations between change in cell abundance on C1D2 vs C1D1 for Plin and Plac. Significant differences were defined as those with a P-value adjusted for multiple testing of P < 0.05.

Result

Following Plac, cell types from myeloid, lymphoid, and erythroid lineage demonstrated significantly decreased abundance on C1D2 vs C1D1, reflecting myelosuppression by Chemo. In contrast, following Plin, an increase in abundance for all GMP-derived myeloid cells (N, M, B, and E) were observed, and in Plin dose-dependent manner. In absolute counts, GMP-derived myeloid cells had increased significantly with Plin at C1D2 vs C1D1, suggesting not only protection, but also stimulation of GMP cells by Plin. Furthermore, significant increases on C1D2 vs C1D1 in immature post-GMP progenitor cells (BAND, metamyelocytes, and myelocytes), were observed with Plin, but not with Plac, further suggesting GMP stimulation by Plin. For CLP and MEP-derived cells, decreases were seen with Plin, however, to a much smaller extent compared to Plac, suggesting some degree of protection with Plin. Cell cluster analysis showed inter-correlation in abundance of GMP-derived cell types (N, M, B, and E), which is in support Lineage Commitment. Relative abundance in cells derived from the CLP and MEP were also intercorrelated with abundance of GMP-derived cells, further supporting Lineage Commitment.

Conclusion

Using bioinformatic analyses, we demonstrated that Plin not only exerts protective, but also stimulatory effects on GMP cells under myelosuppressive conditions. The abundance of immature PBCs derived from the GMPs is in further support of stimulation of GMP cells with Plin. The data also suggests a degree of protective effect with Plin on CLP- and MEP-cells. The interdependence in abundance of mature PBCs derived from GMP cells, but also from CLP- and MEP-derived cells, is strongly supportive of Lineage Commitment.

Mohanlal:BeyondSpring Pharmaceuticals, Inc.: Current Employment. Lu:BeyondSpring Pharmaceuticals, Inc.: Current Employment. Huang:BeyondSpring Pharmaceuticals, In: Current Employment. Honour:BeyondSpring Pharmaceuticals, Inc.: Other: Contract Research Organization. Blayney:BeyondSpring Pharmaceuticals, In: Other: Principle Investigator.