Somatic mutations and clonal expansions in paroxysmal nocturnal hemoglobinuria

In vivo genotoxicity assessment of N-(-9 acridinyl)-b-alanine hydrochloride (S-300) using a validated Pig-a mutagenesis assay

BACKGROUND

N-(-9 acridinyl)-b-alanine hydrochloride (S-300) is the main byproduct of red blood cell (RBC) amustaline/glutathione(GSH) pathogen reduction, currently undergoing phase III US clinical trials following successful European studies(1-3). Phosphatidylinositol glycan, class A (Pig-a) X-linked gene mutagenesis is a validated mammalian in vivo mutation assay for genotoxicity, assessed as clonal loss of glycosylphosphatidylinositol-linked CD59 cell-surface molecules on reticulocytes (RETs) and RBCs.

METHODS

Male Sprague-Dawley rats received continuous infusion of S-300 up to the maximum feasible dose (240 mg/kg/day-limited by solubility and volume) for 28 days. Positive controls received a known mutagen by oral gavage on Days 1-3. Plasma levels of S-300 were assessed by HPLC before, during and after infusion. CD59-negative RBCs and RETs were enumerated in pre-dose and Day 28 samples, using a flow cytometric method. Outcome was evaluated by predetermined criteria using concurrent and historical controls. Toxicity was assessed by laboratory measures and necropsy.

RESULTS

S-300 reached maximum, dose-dependent levels (3-15 μmol/L) within 2-8 h that were sustained for 672 h and undetectable 2 h after infusion. Circulating RET levels indicated a lack of hematopoietic toxicity. Necropsy revealed minimal-mild observations related to poor S-300 solubility at high concentrations. Pig-a assessment met the preset acceptability criteria and revealed no increase in mutant RBCs or RETs.

CONCLUSIONS

Maximum feasible S-300 exposure of rats by continuous infusion for 28 days was not genotoxic as assessed by an Organization for Economic Cooperation and Development-compliant, mammalian, in vivo Pig-a gene mutation assay that meets the requirements of International Conference on Harmonization (ICH) S2(R1) and FDA guidances on genotoxicity testing.

Pegcetacoplan in paroxysmal nocturnal haemoglobinuria: Its use, its clinical effectiveness, and its influence on health-related quality of life and productivity

OBJECTIVES

To describe real-world use/effectiveness of pegcetacoplan (PEG) in paroxysmal nocturnal haemoglobinuria (PNH).

METHODS

Data were drawn from the Adelphi PNH Disease Specific Programme™, a cross-sectional survey conducted in France, Italy, Germany, Spain and the United States from January to November 2022. Patients had a confirmed PNH diagnosis and received PEG for ≥1 month. Physicians reported patient characteristics, treatment use/satisfaction and their perception of patients' fatigue and health-related quality of life (HRQoL). Patients reported treatment satisfaction and completed questionnaires assessing fatigue, HRQoL and productivity. Descriptive statistics were reported.

RESULTS

Overall, 14 physicians provided data for 61 patients who had received 1080 mg/dose PEG for 1.3-14.8 months. At data collection compared to PEG initiation: haemoglobin was 2.5 g/dL higher on average; proportion of patients with lactate dehydrogenase (LDH) ≥1.5 × upper limit of normal was reduced by 27.4%; physician-perceived fatigue was lower and HRQoL better. Physician- and patient-reported treatment satisfaction was high for >90% of patients. Physicians and patients were more satisfied with PEG than previously prescribed C5 complement inhibitors. Mean work impairment and activity impairment in the 7 days prior to data collection were 32.9% and 22.4%, respectively.

CONCLUSIONS

These real-world data support the effectiveness of PEG through positive effects on haemoglobin, LDH, fatigue and HRQoL.

Cytogenetics in the management of bone marrow failure syndromes: Guidelines from the Groupe Francophone de Cytogénétique Hématologique (GFCH)

Bone marrow failure syndromes are rare disorders characterized by bone marrow hypocellularity and resultant peripheral cytopenias. The most frequent form is acquired, so-called aplastic anemia or idiopathic aplastic anemia, an auto-immune disorder frequently associated with paroxysmal nocturnal hemoglobinuria, whereas inherited bone marrow failure syndromes are related to pathogenic germline variants. Among newly identified germline variants, GATA2 deficiency and SAMD9/9L syndromes have a special significance. Other germline variants impacting biological processes, such as DNA repair, telomere biology, and ribosome biogenesis, may cause major syndromes including Fanconi anemia, dyskeratosis congenita, Diamond-Blackfan anemia, and Shwachman-Diamond syndrome. Bone marrow failure syndromes are at risk of secondary progression towards myeloid neoplasms in the form of myelodysplastic neoplasms or acute myeloid leukemia. Acquired clonal cytogenetic abnormalities may be present before or at the onset of progression; some have prognostic value and/or represent somatic rescue mechanisms in inherited syndromes. On the other hand, the differential diagnosis between aplastic anemia and hypoplastic myelodysplastic neoplasm remains challenging. Here we discuss the value of cytogenetic abnormalities in bone marrow failure syndromes and propose recommendations for cytogenetic diagnosis and follow-up.

Case report: Transfusion independence and abolition of extravascular hemolysis in a PNH patient treated with pegcetacoplan

More than half of patients with paroxysmal nocturnal hemoglobinuria (PNH) treated with complement fraction C5 inhibitors experience residual anemia and hemolysis. This is partly due to the persistent activation of the complement cascade upstream C5, resulting in C3 deposition on PNH erythrocytes and extravascular hemolysis in the reticuloendothelial system. Pegcetacoplan is the first proximal C3 inhibitor to be approved for PNH basing on favorable efficacy and safety data in both naïve and eculizumab treated PNH. Here we report the first Italian patient treated with pegcetacoplan in a named patient program. The patient suffered from hemolytic PNH associated with CALR+ myeloproliferative neoplasm and was heavily transfusion dependent despite eculizumab therapy. Treatment with pegcetacoplan induced a dramatic improvement in Hb, along with normalization of unconjugated bilirubin and reticulocytes, as markers of extravascular hemolysis. Sequential laboratory workup showed the disappearance of C3 deposition on erythrocytes by direct anti-globulin test, the increase of PNH clone on erythrocytes, and a peculiar right shift of the ektacytometry curve. The drug was well tolerated, and the patient reported a significant improvement in his quality of life. Overall, pegcetacoplan appears a safe and effective option "ready to use" in the clinic for patients with PNH and suboptimal response to anti-C5 agents.