Small-molecule factor D inhibitors selectively block the alternative pathway of complement in paroxysmal nocturnal hemoglobinuria and atypical hemolytic uremic syndrome.

Paroxysmal nocturnal hemoglobinuria and atypical hemolytic uremic syndrome are diseases of excess activation of the alternative pathway of complement that are treated with eculizumab, a humanized monoclonal antibody against the terminal complement component C5. Eculizumab must be administered intravenously, and moreover some patients with paroxysmal nocturnal hemoglobinuria on eculizumab have symptomatic extravascular hemolysis, indicating an unmet need for additional therapeutic approaches. We report the activity of two novel small-molecule inhibitors of the alternative pathway component Factor D using in vitro correlates of both paroxysmal nocturnal hemoglobinuria and atypical hemolytic uremic syndrome. Both compounds bind human Factor D with high affinity and effectively inhibit its proteolytic activity against purified Factor B in complex with C3b. When tested using the traditional Ham test with cells from paroxysmal nocturnal hemoglobinuria patients, the Factor D inhibitors significantly reduced complement-mediated hemolysis at concentrations as low as 0.01 µM. Additionally the compound ACH-4471 significantly decreased C3 fragment deposition on paroxysmal nocturnal hemoglobinuria erythrocytes, indicating a reduced potential relative to eculizumab for extravascular hemolysis. Using the recently described modified Ham test with serum from patients with atypical hemolytic uremic syndrome, the compounds reduced the alternative pathway-mediated killing of PIGA-null reagent cells, thus establishing their potential utility for this disease of alternative pathway of complement dysregulation and validating the modified Ham test as a system for pre-clinical drug development for atypical hemolytic uremic syndrome. Finally, ACH-4471 blocked alternative pathway activity when administered orally to cynomolgus monkeys. In conclusion, the small-molecule Factor D inhibitors show potential as oral therapeutics for human diseases driven by the alternative pathway of complement, including paroxysmal nocturnal hemoglobinuria and atypical hemolytic uremic syndrome.

Minimal Residual Disease Data in Hematologic Malignancy Drug Applications and Labeling: An FDA Perspective.

Minimal residual disease (MRD) is increasingly used as a prognostic biomarker, a measure of clinical efficacy, and a guide for treatment decisions in various hematologic malignancies. We sought to characterize MRD data in registrational trials in hematologic malignancies submitted to the U.S. Food and Drug Administration (FDA) with the ultimate goal of expanding the utility of MRD data in future drug applications. We descriptively analyzed MRD data collected in registrational trials, including the type of MRD endpoint, assay, disease compartment(s) assessed, and the acceptance of MRD data in the U.S. prescribing information (USPI). Of 196 drug applications submitted between January 2014 and February 2021, 55 (28%) included MRD data. Of the 55 applications, MRD data was proposed by the Applicant for inclusion in the USPI in 41 (75%) applications but was included in only 24 (59%). Despite an increasing number of applications that proposed to include MRD data in the USPI, the acceptance rate decreased over time. Although MRD data have the potential to expedite drug development, our analysis identified challenges and specific areas for improvement, including assay validation, standardization of collection methods to optimize performance, and considerations in trial design and statistical methodology.

Trends in the approval of cancer therapies by the FDA in the twenty-first century.

The cancer treatment landscape has changed dramatically since the turn of the century, resulting in substantial improvements in outcomes for patients. This Review summarizes trends in the approval of oncology therapeutic products by the United States Food and Drug Administration (FDA) from January 2000 to October 2022, based on a categorization of these products by their mechanism of action and primary target. Notably, the rate of oncology indication approvals has increased in this time, driven by approvals for targeted therapies, as has the rate of introduction of new therapeutic approaches. Kinase inhibitors are the dominant product class by number of approved products and indications, yet immune checkpoint inhibitors have the second most approvals despite not entering the market until 2011. Other trends include a slight increase in the share of approvals for biomarker-defined populations and the emergence of tumour-site-agnostic approvals. Finally, we consider the implications of the trends for the future of oncology therapeutic product development, including the impact of novel therapeutic approaches and technologies.

Receptor-mediated protein transport in the early secretory pathway.

Many secretory proteins are thought to rely upon transmembrane cargo receptors for efficient endoplasmic reticulum (ER)-to-Golgi transport. These receptors recognize specific cargo-encoded sorting signals. Only a few such cargo receptors have been characterized in detail, most of them in yeast. The only well-defined cargo receptor from mammalian cells, the LMAN1-MCFD2 complex, is required for the efficient secretion of coagulation factors V and VIII. Studies of this complex, coupled with recent advances in elucidating the basic machinery that mediates ER-to-Golgi transport, have provided a more-detailed picture of the mechanisms underlying receptor-mediated transport in the early secretory pathway. In addition to yeast studies, insights have also come from investigations into several inherited disorders that have recently been attributed to defects in the secretory pathway.

FDA Approval Summary: Belantamab Mafodotin for Patients with Relapsed or Refractory Multiple Myeloma.

On August 5, 2020, the FDA granted accelerated approval to belantamab mafodotin-blmf (BLENREP; GlaxoSmithKline) for the treatment of adult patients with relapsed or refractory multiple myeloma who have received at least four prior therapies including an anti-CD38 monoclonal antibody, a proteasome inhibitor, and an immunomodulatory agent. Substantial evidence of effectiveness was obtained from the phase II, multicenter DREAMM-2 trial. Patients received belantamab mafodotin 2.5 or 3.4 mg/kg intravenously once every 3 weeks until disease progression or unacceptable toxicity. The trial demonstrated an overall response rate of 31% in the 2.5 mg/kg cohort and 34% in the 3.4 mg/kg cohort. Keratopathy was the most frequent adverse event, occurring in 71% and 77% of patients, respectively. Other ocular toxicities included changes in visual acuity, blurred vision, and dry eye. The U.S. prescribing information for belantamab mafodotin includes a boxed warning for ocular toxicity, and belantamab mafodotin is available only through a restricted program under a Risk Evaluation and Mitigation Strategy. This article summarizes the data and the FDA review process supporting accelerated approval of belantamab mafodotin 2.5 mg/kg intravenously once every 3 weeks. This approval may be contingent upon verification and description of clinical benefit in confirmatory trial(s).

Analysis of racial and ethnic disparities in multiple myeloma US FDA drug approval trials.

African Americans (AAs) have a higher incidence of multiple myeloma (MM) than White patients. Mortality is also higher in AAs compared with White patients. AAs more commonly have immunoglobulin H translocations t(11;14) and t(14;16) compared with White patients. We sought to characterize the demographic representation in MM clinical trials and evaluate outcomes based on race and ethnicity. We conducted a pooled analysis of all trials submitted to the US Food and Drug Administration (FDA) to support approval of a MM therapeutic between 2006 and 2019. Demographic characteristics were analyzed descriptively. An age-adjusted stratified Cox regression model was used to evaluate the relationship between time-to-event outcomes and race and ethnicity. Nineteen global trials comprising 10 157 patients were pooled. White, Asian, and Black patients comprised 84%, 7%, and 4% of the dataset, respectively; Hispanic patients comprised 4%. The age-adjusted overall survival hazard ratio (HR) for Black compared with White patients was 0.89 (95% confidence interval [CI], 0.75-1.05). The age-adjusted HR for US Black vs US White patients was 0.82 (95% CI, 0.66-1.02). For rest-of-world (RoW) Black vs RoW White patients, the HR was 1.31 (95% CI, 0.97-1.77). Black and Hispanic patients were underrepresented in the trials supporting FDA approval of MM drugs. Black patients were primarily enrolled in the United States. Outcomes in US patients were more favorable compared with those in patients in the RoW. Given the higher incidence of MM in AAs and the different disease characteristics, efforts should be made to improve representation of AAs in MM clinical trials.

Perspectives on Drug Development in Multiple Myeloma-Looking Forward to 2025.

The multiple myeloma treatment landscape has evolved considerably over the last 20 years with the development of multiple therapies with novel mechanisms of action and new combination regimens. However, the recent failure of several large phase III trials, coupled with an increased understanding of the mutational landscape of multiple myeloma has provided opportunities to explore optimal strategies for future multiple myeloma drug development. The Office of Oncologic Diseases at the FDA held an educational symposium, "Drug Development in MM-Project 2025," in November 2019. The symposium brought together select U.S.-based academic thought leaders in the field of multiple myeloma to explore issues relevant to regulatory science in the field, including considerations for trial design, combination strategies, control arms, and precision medicine. This article summarizes the highlights of this educational symposium held at the FDA, including discussions on the future development of novel drugs and drug combinations and biomarker-directed therapies for patients with multiple myeloma.

Germline mutations in the alternative pathway of complement predispose to HELLP syndrome.

BACKGROUND: HELLP (hemolysis, elevated liver enzymes, and low platelets) syndrome is a severe variant of hypertensive disorders of pregnancy affecting approximately 1% of all pregnancies, and has significant maternal and fetal morbidity. Previously, we showed that upregulation of the alternative pathway of complement (APC) plays a role in HELLP syndrome. We hypothesize that HELLP syndrome follows a 2-hit disease model similar to atypical hemolytic uremic syndrome (aHUS), requiring both genetic susceptibility and an environmental risk factor. Our objective was to perform a comparative analysis of the frequency of APC activation and germline mutations in affected women and to create a predictive model for identifying HELLP syndrome. METHODS: Pregnant women with HELLP syndrome, and healthy controls after 23 weeks of gestation were recruited, along with aHUS and thrombotic thrombocytopenic purpura participants. We performed a functional assay, the mHam, and targeted genetic sequencing in all groups. RESULTS: Significantly more participants with rare germline mutations in APC genes were present in the HELLP cohort compared with controls (46% versus 8%, P = 0.01). In addition, significantly more HELLP participants were positive for the mHam when compared with controls (62% versus 16%, P = 0.009). Testing positive for both a germline mutation and the mHam was highly predictive for the diagnosis of HELLP syndrome. CONCLUSION: HELLP syndrome is characterized by both activation of the APC and frequent germline mutations in APC genes. Similar to aHUS, treatment via complement inhibition to mitigate maternal and fetal morbidity and mortality may be possible. FUNDING: National Heart Lung and Blood Institute grants T32HL007525 and R01HL133113.

Complementopathies.

The complement system is an essential part of the innate immune system that requires careful regulation to ensure responses are appropriately directed against harmful pathogens, while preventing collateral damage to normal host cells and tissues. While deficiency in some components of the complement pathway is associated with increased susceptibility to certain infections, it has also become clear that inappropriate activation of complement is an important contributor to human disease. A number of hematologic disorders are driven by complement, and these disorders may be termed "complementopathies". This includes paroxysmal nocturnal hemoglobinuria (PNH), atypical hemolytic uremic syndrome (aHUS), cold agglutinin disease (CAD) and other related disorders, which will be the focus of this review. A better understanding of the central role of the complement system in the pathophysiology of these disorders may allow for application of therapies directed at blocking the complement cascade.

A hypomorphic PIGA gene mutation causes severe defects in neuron development and susceptibility to complement-mediated toxicity in a human iPSC model.

Mutations in genes involved in glycosylphosphatidylinositol (GPI) anchor biosynthesis underlie a group of congenital syndromes characterized by severe neurodevelopmental defects. GPI anchored proteins have diverse roles in cell adhesion, signaling, metabolism and complement regulation. Over 30 enzymes are required for GPI anchor biosynthesis and PIGA is involved in the first step of this process. A hypomorphic mutation in the X-linked PIGA gene (c.1234C>T) causes multiple congenital anomalies hypotonia seizure syndrome 2 (MCAHS2), indicating that even partial reduction of GPI anchored proteins dramatically impairs central nervous system development, but the mechanism is unclear. Here, we established a human induced pluripotent stem cell (hiPSC) model containing the PIGAc.1234C>T mutation to study the effects of a hypomorphic allele of PIGA on neuronal development. Neuronal differentiation from neural progenitor cells generated by EB formation in PIGAc.1234C>T is significantly impaired with decreased proliferation, aberrant synapse formation and abnormal membrane depolarization. The results provide direct evidence for a critical role of GPI anchor proteins in early neurodevelopment. Furthermore, neural progenitors derived from PIGAc.1234C>T hiPSCs demonstrate increased susceptibility to complement-mediated cytotoxicity, suggesting that defective complement regulation may contribute to neurodevelopmental disorders.

Disruption of the Sec24d gene results in early embryonic lethality in the mouse.

Transport of newly synthesized proteins from the endoplasmic reticulum (ER) to the Golgi is mediated by the coat protein complex COPII. The inner coat of COPII is assembled from heterodimers of SEC23 and SEC24. Though mice with mutations in one of the four Sec24 paralogs, Sec24b, exhibit a neural tube closure defect, deficiency in humans or mice has not yet been described for any of the other Sec24 paralogs. We now report characterization of mice with targeted disruption of Sec24d. Early embryonic lethality is observed in mice completely deficient in SEC24D, while a hypomorphic Sec24d allele permits survival to mid-embryogenesis. Mice haploinsufficient for Sec24d exhibit no phenotypic abnormality. A BAC transgene containing Sec24d rescues the embryonic lethality observed in Sec24d-null mice. These results demonstrate an absolute requirement for SEC24D expression in early mammalian development that is not compensated by the other three Sec24 paralogs. The early embryonic lethality resulting from loss of SEC24D in mice contrasts with the previously reported mild skeletal phenotype of SEC24D deficiency in zebrafish and restricted neural tube phenotype of SEC24B deficiency in mice. Taken together, these observations suggest that the multiple Sec24 paralogs have developed distinct functions over the course of vertebrate evolution.

Expression of the blood-group-related glycosyltransferase B4galnt2 influences the intestinal microbiota in mice.

Glycans on mucosal surfaces have an important role in host-microbe interactions. The locus encoding the blood-group-related glycosyltransferase ß-1,4-N-acetylgalactosaminyltransferase 2 (B4galnt2) is subject to strong selective forces in natural house-mouse populations that contain a common allelic variant that confers loss of B4galnt2 gene expression in the gastrointestinal (GI) tract. We reasoned that altered glycan-dependent intestinal host-microbe interactions may underlie these signatures of selection. To determine whether B4galnt2 influences the intestinal microbial ecology, we profiled the microbiota of wild-type and B4galnt2-deficient siblings throughout the GI tract using 16S rRNA gene pyrosequencing. This revealed both distinct communities at different anatomic sites and significant changes in composition with respect to genotype, indicating a previously unappreciated role of B4galnt2 in host-microbial homeostasis. Among the numerous B4galnt2-dependent differences identified in the abundance of specific bacterial taxa, we unexpectedly detected a difference in the pathogenic genus, Helicobacter, suggesting Helicobacter spp. also interact with B4galnt2 glycans. In contrast to other glycosyltransferases, we found that the host intestinal B4galnt2 expression is not dependent on presence of the microbiota. Given the long-term maintenance of alleles influencing B4galnt2 expression by natural selection and the GI phenotypes presented here, we suggest that variation in B4galnt2 GI expression may alter susceptibility to GI diseases such as infectious gastroenteritis.

Similar regulation of cell surface human T-cell leukemia virus type 1 (HTLV-1) surface binding proteins in cells highly and poorly transduced by HTLV-1-pseudotyped virions.

Little is known about the requirements for human T-cell leukemia virus type 1 (HTLV-1) entry, including the identity of the cellular receptor(s). Previous studies have shown that although the HTLV receptor(s) are widely expressed on cell lines of various cell types from different species, cell lines differ dramatically in their susceptibility to HTLV-Env-mediated fusion. Human cells (293, HeLa, and primary CD4(+) T cells) showed higher levels of binding at saturation than rodent (NIH 3T3 and NRK) cells to an HTLV-1 SU immunoadhesin. A direct comparison of the binding of the HTLV-1 surface glycoprotein (SU) immunoadhesin and transduction by HTLV-1 pseudotyped virus revealed parallels between the level of binding and the titer for various cell lines. When cells were treated with phorbol myristate acetate (PMA), which down-modulates a number of cell surface molecules, the level of SU binding was markedly reduced. However, PMA treatment only slightly reduced the titer of murine leukemia virus(HTLV-1) on both highly susceptible and poorly susceptible cells. Treatment of target cells with trypsin greatly reduced binding, indicating that the majority of HTLV SU binding is to proteins. Polycations, which enhance the infectivity of several other retroviruses, inhibited HTLV-1 Env-mediated binding and entry on both human and rodent cells. These results suggest that factors other than the number of primary binding receptors are responsible for the differences in the titers of HTLV-1 pseudotypes between highly susceptible cells and poorly susceptible cells.