Compassionate Use Narsoplimab for Severe Refractory Transplantation-Associated Thrombotic Microangiopathy in Children

Transplant-associated thrombotic microangiopathy (TA-TMA) is a common and potentially severe complication of hematopoietic cell transplantation. TA-TMA-directed therapy with eculizumab, a complement C5 inhibitor, has resulted in a survival benefit in some studies. However, children with TA-TMA refractory to C5 inhibition with eculizumab (rTA-TMA) have mortality rates exceeding 80%, and there are no other known therapies. Narsoplimab, an inhibitor of the MASP-2 effector enzyme of the lectin pathway, has been studied in adults with TA-TMA as first-line therapy with a response rate of 61%. Although there are limited data on narsoplimab use as a second-line agent in children, we hypothesized, that complement pathways proximal to C5 are activated in rTA-TMA, and that narsoplimab may ameliorate rTA-TMA in children. In this single-center study, children were enrolled on single-patient, Institutional Review Board-approved compassionate use protocols for narsoplimab treatment. Clinical complement lab tests were obtained at the discretion of the treating physician, although all patients were also offered participation in a companion biomarker study. Research blood samples were obtained at the time of TA-TMA diagnosis, prior to eculizumab treatment, at the time of refractory TA-TMA diagnosis prior to the first narsoplimab dose, and 2 weeks after the first narsoplimab dose. Single ELISA kits were used to measure markers of complement activation according to the manufacture's instructions. Five children with rTA-TMA received narsoplimab; 3 were in multiorgan failure and 2 had worsening multiorgan dysfunction at the time of treatment. Additional comorbidities at the time of treatment included sinusoidal obstructive syndrome (SOS; n = 3), viral infection (n = 3), and steroid-refractory stage 4 lower gut grade IV acute graft-versus-host disease (aGVHD, n = 3). Two infants with concurrent SOS and no aGVHD had resolution of organ dysfunction; 1 also developed transfusion-independence (complete response), and the other's hematologic response was not assessable in the setting of leukemia and chemotherapy (partial response). One additional patient achieved transfusion independence but had no improvement in organ manifestations (partial response), and 2 patients treated late in the course of disease had no response. Narsoplimab was well tolerated without any attributed adverse effects. Three patients consented to provide additional research blood samples. One patient with resolution of organ failure demonstrated evidence of proximal pathway activation prior to narsoplimab treatment with subsequent declines in Ba, Bb, C3a, and C5a and increases in C3 in both clinical and research lab tests. Otherwise, there was no clear pattern of other complement markers, including MASP-2 levels, after therapy. In this cohort of ill children with rTA-TMA and multiple comorbidities, 3 patients benefited from narsoplimab. Notably, the 2 patients with resolution of organ involvement did not have steroid-refractory aGVHD, which is thought to be a critical driver of TA-TMA. Additional studies are needed to determine which patients are most likely to benefit from narsoplimab and which markers may be most helpful for monitoring lectin pathway activation and inhibition.

Rational use of eculizumab in secondary atypical hemolytic uremic syndrome

Background

Secondary atypical hemolytic uremic syndrome (secondary aHUS) is a heterogeneous group of thrombotic microangiopathies (TMA) associated with various underlying conditions. Unlike primary aHUS, there is still no hard evidence on the efficacy of complement blockade in secondary aHUS, since the two main series that investigated this subject showed discrepant results. Our work aims to reassess the efficacy of eculizumab in treating secondary aHUS.

Methods

Observational, retrospective, single-center study, in which we analyzed the hematological and renal evolution of 23 patients diagnosed with secondary aHUS who received treatment with eculizumab and compared them with a control cohort of 14 patients. Complete renal response was defined as the recovery of renal function before the event, partial renal response as a recovery of 50% of lost glomerular filtration rate, and hematological response as normalization of hemoglobin and platelets.

Results

We found no statistically significant differences in baseline characteristics or disease severity between both groups. After a median of 5 doses of eculizumab, the group of patients who received complement blockade presented a significant difference in renal response (complete in 52.3% of patients and partial in 23.8%) compared to the control cohort (complete response 14.3% and partial of 14.3%). Rates of hematological remission were similar in both groups (90.9% in the eculizumab cohort and 85.7% in the control cohort).

Conclusion

Early and short-term use of eculizumab in patients with secondary aHUS could be an effective and safe therapeutic option, assuring better renal recovery compared to patients who do not receive complement blockade.

Use of patient-reported outcomes (PRO) data to complement exposure-response analysis in early clinical cancer drug development

BACKGROUND

This proof-of-concept retrospective case study investigated whether patient-reported outcomes (PRO) instruments, designed to capture symptomatic adverse event data, could identity a known exposure-response (ER) relationship for safety characterized in an original FDA analysis of an approved anti-cancer agent. PRO instruments have been designed to uniquely quantify the tolerability aspects of exposure-associated symptomatic adverse events. We explored whether standard ER analyses of clinician-reported safety data for symptomatic adverse events could be complemented by ER analysis using PRO data that capture and quantify the tolerability aspects of these same symptomatic adverse events.

METHODS

Exposure-associated adverse event data for diarrhea were analyzed in parallel in 120 patients enrolled in a clinical trial using physician reported Common Terminology Criteria for Adverse Events (CTCAE) and patient-reported symptomatic adverse event data captured by the National Cancer Institute's (NCI) PRO Common Terminology Criteria for Adverse Events (PRO-CTCAE) instrument. Comparative ER analyses of diarrhea were conducted using the same dataset. Results from the CTCAE and PRO-CTCAE ER analyses were assessed for consistency with the ER relationship for diarrhea established in the original NDA using a 750-patient dataset. The analysis was limited to the 120-patient subset with parallel CTCAE and PRO-CTCAE assessments.

RESULTS

Within the same 120-patient dataset, ER analysis using dense, longitudinal PRO-CTCAE-derived data was sensitive to identify the known ER relationship for diarrhea, whereas the standard CTCAE based ER analysis was not.

CONCLUSIONS

ER analysis using PRO assessed symptomatic adverse event data may be a sensitive tool to complement traditional ER analysis. Improved identification of relationships for safety, by including quantification of the tolerability aspect of symptomatic adverse events using PRO instruments, may be useful to improve the sensitivity of exposure response analysis to support early clinical trial dosage optimization strategies, where decision making occurs within limited small patient datasets.

Pozelimab: First Approval

Pozelimab (pozelimab-bbfg; VEOPOZ™) is a fully human immunoglobulin (Ig) G4P (i.e. IgG4 with a proline substitution to promote stabilization of the disulfide bonds between the two heavy chains) monoclonal antibody developed by Regeneron Pharmaceuticals Inc., to block the activity of complement factor 5 (C5) and prevent diseases mediated by the complement pathway. In August 2023, pozelimab received its first approval for the treatment of adults, and paediatric patients aged ≥ 1 year with CD55-deficient protein-losing enteropathy (PLE), also known as CHAPLE disease, in the USA. It is the first US FDA-approved treatment for this disease. In the USA, pozelimab has been granted orphan drug designations for the treatment of paroxysmal nocturnal haemoglobinuria (PNH) [both as a monotherapy and in combination with cemdisiran] and for the treatment of myasthenia gravis (in combination with cemdisiran). Pozelimab is also undergoing clinical development in several other countries worldwide for the treatment of CD55-deficient PLE, PNH and myasthenia gravis. This article summarizes the milestones in the development of pozelimab leading to this first approval for the treatment of adults, and paediatric patients aged ≥ 1 year with CD55-deficient PLE, also known as CHAPLE disease, in the USA.

Fc-mediated functions of nirsevimab complement direct respiratory syncytial virus neutralization but are not required for optimal prophylactic protection

Introduction

Nirsevimab is an extended half-life (M252Y/S254T/T256E [YTE]-modified) monoclonal antibody to the pre-fusion conformation of the respiratory syncytial virus (RSV) Fusion protein, with established efficacy in preventing RSV-associated lower respiratory tract infection in infants for the duration of a typical RSV season. Previous studies suggest that nirsevimab confers protection via direct virus neutralization. Here we use preclinical models to explore whether fragment crystallizable (Fc)-mediated effector functions contribute to nirsevimab-mediated protection.

Methods

Nirsevimab, MEDI8897* (i.e., nirsevimab without the YTE modification), and MEDI8897*-TM (i.e., MEDI8897* without Fc effector functions) binding to Fc γ receptors (FcγRs) was evaluated using surface plasmon resonance. Antibody-dependent neutrophil phagocytosis (ADNP), antibody-dependent cellular phagocytosis (ADCP), antibody-dependent complement deposition (ADCD), and antibody-dependent cellular cytotoxicity (ADCC) were assessed through in vitro and ex vivo serological analyses. A cotton rat challenge study was performed with MEDI8897* and MEDI8897*-TM to explore whether Fc effector functions contribute to protection from RSV.

Results

Nirsevimab and MEDI8897* exhibited binding to a range of FcγRs, with expected reductions in FcγR binding affinities observed for MEDI8897*-TM. Nirsevimab exhibited in vitro ADNP, ADCP, ADCD, and ADCC activity above background levels, and similar ADNP, ADCP, and ADCD activity to palivizumab. Nirsevimab administration increased ex vivo ADNP, ADCP, and ADCD activity in participant serum from the MELODY study (NCT03979313). However, ADCC levels remained similar between nirsevimab and placebo. MEDI8897* and MEDI8897*-TM exhibited similar dose-dependent reduction in lung and nasal turbinate RSV titers in the cotton rat model.

Conclusion

Nirsevimab possesses Fc effector activity comparable with the current standard of care, palivizumab. However, despite possessing the capacity for Fc effector activity, data from RSV challenge experiments illustrate that nirsevimab-mediated protection is primarily dependent on direct virus neutralization.

Geographic atrophy: Mechanism of disease, pathophysiology, and role of the complement system

Geographic atrophy (GA) is an advanced form of age-related macular degeneration (AMD), characterized by atrophic lesions that first start in the outer retina and progressively expand to cover the macula and the fovea, the center of the macula, leading to irreversible loss of vision over time. GA is distinct from wet or neovascular AMD (nAMD), the other form of advanced AMD. Neovascular AMD is characterized by new invading leaky blood vessels in the macula that can lead to acute vision loss. GA and nAMD may coexist in the same eye. The underlying pathophysiology of GA is complex and thought to involve chronic inflammation due to overactivation of the complement system that leads to the loss of photoreceptors, retinal pigment epithelium (RPE), and the underlying choriocapillaris. The disappearance of these structures appears as sharply demarcated atrophic lesions that are typical of GA. Researchers have reported about 1 million reported cases of GA in the United States, and about 160,000 cases occur per year. The most important risk factors for GA are increasing age and family history. Diagnosis of GA is usually made by using multimodal imaging techniques. Lesions associated with GA are highly heterogeneous, and the growth rate may differ from patient to patient. Despite the progressive nature of GA, the fovea may be spared until much later in the disease, thereby retaining central vision in patients. With time, atrophic lesions may progressively grow to involve the fovea, thereby severely impairing central vision. Vision loss can happen rapidly once the lesions reach the fovea. However, even without the involvement of the fovea, ongoing vision impairment impacting daily life may be present. Median time from GA not involving the center of the fovea (without subfoveal involvement) to GA with lesion boundary affecting the foveal center (subfoveal involvement) ranges from 1.4 to 2.5 years. GA can greatly impact patients' functioning and quality of life and limit their independence by interfering with activities of daily living, including difficulties with reading, driving, watching television, recognizing faces, and being unable to do household chores. No treatments have been available until intravitreal pegcetacoplan was recently approved by the US Food and Drug Administration for GA secondary to AMD. DISCLOSURES: Dr Bakri serves as a consultant to Apellis Pharmaceuticals, as well as AbbVie, Adverum, Eyepoint, iLumen, Iveric Bio, Genentech, Novartis, Outlook Therapeutics, Pixium, Regeneron, Roche, and Regenxbio. Drs Sharp, Luo, and Sarda are employees of Apellis Pharmaceuticals. Dr Bektas and Ms Khan are employees of RTI Health Solutions. Apellis developed and led the concept design of this publication, review and interpretation, approval, and decision to publish. This research was developed under a research contract between RTI Health Solutions and Apellis Pharmaceuticals and was funded by Apellis Pharmaceuticals. This supplement is to describe the disease of geographic atrophy and was funded by Apellis. Apellis Pharmaceuticals has developed Syfovre (pegcetacoplan), the first and only treatment for geographic atrophy.

Complement as a vital nexus of the pathobiological connectome for acute respiratory distress syndrome: An emerging therapeutic target

The hallmark of acute respiratory distress syndrome (ARDS) pathobiology is unchecked inflammation-driven diffuse alveolar damage and alveolar-capillary barrier dysfunction. Currently, therapeutic interventions for ARDS remain largely limited to pulmonary-supportive strategies, and there is an unmet demand for pharmacologic therapies targeting the underlying pathology of ARDS in patients suffering from the illness. The complement cascade (ComC) plays an integral role in the regulation of both innate and adaptive immune responses. ComC activation can prime an overzealous cytokine storm and tissue/organ damage. The ARDS and acute lung injury (ALI) have an established relationship with early maladaptive ComC activation. In this review, we have collected evidence from the current studies linking ALI/ARDS with ComC dysregulation, focusing on elucidating the new emerging roles of the extracellular (canonical) and intracellular (non-canonical or complosome), ComC (complementome) in ALI/ARDS pathobiology, and highlighting complementome as a vital nexus of the pathobiological connectome for ALI/ARDS via its crosstalking with other systems of the immunome, DAMPome, PAMPome, coagulome, metabolome, and microbiome. We have also discussed the diagnostic/therapeutic potential and future direction of ALI/ARDS care with the ultimate goal of better defining mechanistic subtypes (endotypes and theratypes) through new methodologies in order to facilitate a more precise and effective complement-targeted therapy for treating these comorbidities. This information leads to support for a therapeutic anti-inflammatory strategy by targeting the ComC, where the arsenal of clinical-stage complement-specific drugs is available, especially for patients with ALI/ARDS due to COVID-19.

[Novel therapeutic agents for hemolytic anemia]

In recent years, it has become clear that various diseases are caused by complement (related molecule) abnormalities (complementopathies) or are exacerbated by complement (complement-related diseases), and novel therapeutic agents targeting complement (anti-complement agents) are now being developed. Paroxysmal nocturnal hemoglobinuria (PNH) is a hematopoietic stem cell disorder characterized by complement-mediated intravascular hemolysis due to a deficiency of complement regulatory factors, making it a perfect candidate for anti-complement agents. In 2007, the anti-C5 monoclonal antibody eculizumab was approved for PNH, as the first anti-complement agent. The indications for eculizumab are expanding, and aggressive development is underway for new anti-complement agents, not only for PNH but also a variety of other diseases. In addition, the anti-C1s antibody sutimlimab was approved last year for the treatment of cold agglutinin disease, a form of autoimmune hemolytic anemia. This presentation overviews novel anti-complement agents for these hemolytic anemias.

The Complement System and ANCA Associated Vasculitis in the Era of Anti-Complement Drugs

ANCA (anti-neutrophil cytoplasmic antibody)-associated vasculitis (AAV) is the condition in which ANCA, as an autoantibody, is associated with the pathogenesis of vasculitis in small blood vessels, mainly in the ear, nose, throat, kidney, lung, and nerves. These diseases are important because they can be fatal due to renal failure and pulmonary hemorrhage if not promptly and appropriately treated. Recently accumulated evidence has shown that C5a produced by the complement alternative pathway primes neutrophils, which in turn activate the complement alternative pathway, leading to the pathogenesis of AAV. Avacopan (CCX168), a C5aR antagonist was shown to be effective against AAV, and it has been a novel therapeutic option, becoming a novel anti-complement drug to modulate inflammatory diseases.

[Research Advances on the Pathogenesis and Treatment of Hemolytic Uremic Syndrome --Review]

Hemolytic uremic syndrome (HUS) is clinically rare, with high mortality and case fatality rates. In recent years, the research on HUS has been intensified and the pathophysiological mechanism has been continuously improved. At present, the main mechanism of pathogenesis is the excessive activation of complement alternative pathways mediated by complement-related gene mutations or the existence of antibodies. The treatment methods and strategies are also constantly updated, mainly including complement-blocking drugs such as Eculizumab, Lavalizumab, and Ravulizumab. In this review, the new developments in the pathogenesis and treatment of HUS is summarized, and provide references for the clinical treatment of HUS.

Complement Therapeutics in the Multi-Organ Donor: Do or Don't?

Over the last decade, striking progress has been made in the field of organ transplantation, such as better surgical expertise and preservation techniques. Therefore, organ transplantation is nowadays considered a successful treatment in end-stage diseases of various organs, e.g. the kidney, liver, intestine, heart, and lungs. However, there are still barriers which prevent a lifelong survival of the donor graft in the recipient. Activation of the immune system is an important limiting factor in the transplantation process. As part of this pro-inflammatory environment, the complement system is triggered. Complement activation plays a key role in the transplantation process, as highlighted by the amount of studies in ischemia-reperfusion injury (IRI) and rejection. However, new insight have shown that complement is not only activated in the later stages of transplantation, but already commences in the donor. In deceased donors, complement activation is associated with deteriorated quality of deceased donor organs. Of importance, since most donor organs are derived from either brain-dead donors or deceased after circulatory death donors. The exact mechanisms and the role of the complement system in the pathophysiology of the deceased donor have been underexposed. This review provides an overview of the current knowledge on complement activation in the (multi-)organ donor. Targeting the complement system might be a promising therapeutic strategy to improve the quality of various donor organs. Therefore, we will discuss the complement therapeutics that already have been tested in the donor. Finally, we question whether complement therapeutics should be translated to the clinics and if all organs share the same potential complement targets, considering the physiological differences of each organ.

Complement in immune and inflammatory disorders: therapeutic interventions

With the awareness that immune-inflammatory cross-talk is at the heart of many disorders, the desire for novel immunomodulatory strategies in the therapy of such diseases has grown dramatically. As a prime initiator and important modulator of immunological and inflammatory processes, the complement system has emerged as an attractive target for early and upstream intervention in inflammatory diseases and has moved into the spotlight of drug discovery. Although prevalent conditions such as age-related macular degeneration have attracted the most attention, the diverse array of complement-mediated pathologies, with distinct underlying mechanisms, demands a multifaceted arsenal of therapeutic strategies. Fortunately, efforts in recent years have not only introduced the first complement inhibitors to the clinic but also filled the pipelines with promising candidates. With a focus on immunomodulatory strategies, in this review we discuss complement-directed therapeutic concepts and highlight promising candidate molecules.

The role of complement in stroke therapy

Cerebral ischemia and reperfusion initiate an inflammatory process which results in secondary neuronal damage. Immunomodulatory agents represent a promising means of salavaging viable tissue following stroke. The complement cascade is a potent mediator of inflammation which is activated following cerebral ischemia. Complement is deposited on apoptotic neurons which likely leads to injury in adjacent viable cells. Studies suggest that blocking the complement cascade during the early phases of infarct evolution may result in decreased penumbral tissue infarction and limit the extent of brain injury. Additionally, other elements of the complement cascade may play a critical role in cell survival. In this paper, we review the role of the complement cascade in neuronal damage following ischemic injury and emphasize possible therapeutic targets.

Complement and its breakdown products in SLE

The complement system has important protective functions in both the innate and the adaptive immune systems but can also, when inappropriately activated, cause tissue damage. Complement deficiency predisposes to infection and also to development of autoimmune disease, especially SLE, and complement is at the same time involved in the pathogenesis of this disease. In this review, various aspects of this dualism are discussed. An overview of activation pathways and activation products is given, together with a description of autoimmunity against complement and the potential of complement regulation in future therapeutics.

Cardiac protection by pharmacological modulation of inflammation

Inflammation is a reaction to primary injury of various kinds, such as infection and trauma, which has both beneficial and detrimental effects. Inflammation has been associated with major diseases of the heart and vessels. Research has focused not only on ischaemia but also on post-ischaemic reperfusion, which is known to activate and amplify the inflammatory response. Although reperfusion should always be attempted in the clinical environment, it has been shown experimentally that it can cause some cardiac damage, in addition to that caused by ischaemia. Therefore, it is reasonable to attempt to increase the benefit obtainable with reperfusion by modulating inflammatory processes triggered by reperfusion itself. In this field, different potential therapeutic targets have been identified and interventions have been tested over the last 30 years. With the exception of adenosine, which probably does not act merely through inhibition of the inflammatory response, no other compounds have yet proven successful in clinical trials. Active research is ongoing. Broadening the approach from the heart to the cardiovascular system, promising data is emerging on cardiovascular protection conferred by statins in patients with coronary heart disease (CHD) and high levels of C-reactive protein (CRP), a systemic marker of inflammation. Similarly, results of trials aimed at preventing cardiovascular events by eradicating chronic infections will be among the first to directly test whether such therapies will decrease risks of cardiovascular disease.

Autologous bone marrow transplantation for high risk acute lymphoblastic leukemia: clinical relevance of ex vivo bone marrow purging with monoclonal antibodies and complement

Herein we describe our experience with 75 consecutive autologous BM transplants for patients with high-risk ALL, with special attention to the clinical impact of BM purging. Fifty-two patients received purged BM using monoclonal antibody (MoAb) cocktails and complement, and 23 patients received untreated BM. The distribution of prognostic factors was similar in both groups. Hemopoietic reconstitution was adequate and did not differ in the two groups. Transplant-related mortality was 9.6% and 13% in 'purged' and 'unpurged' groups. Median follow up was 11 months (2-71) and overall actuarial probability of disease-free survival (DFS) at 5 years was 40% (53% relapse probability). We found a beneficial effect of purging in patients over 15 years of age and in patients needing more than 1 month to reach CR1. Patients in CR1 receiving purged marrow had a longer DFS and a lower relapse probability (52% vs 12%, P = 0.02 and 35% vs 86%, P = 0.005, respectively) which were related to the efficacy of the purging procedure (more or less than one log of depletion). In further CR, no advantage of purging has been found. Our data strongly suggest the clinical relevance of BM purging in autologous BMT in high-risk ALL patients and support the need for prospective randomized studies.

Immunologically based methods for the elimination of tumor cells from autologous stem cell grafts

There is currently renewed interest in the potential of tumor cells within autologous hematopoietic grafts to contribute to relapse of cancer post-transplant. This has prompted the development of a wide variety of techniques for the ex vivo removal or purging of malignant cells from bone marrow and peripheral blood progenitor cell grafts. Both negative selection, in which tumor cells are eliminated, and positive selection, in which hematopoietic stem cells are enriched, are under examination as purging modalities. This review describes the use of immunologically based methods for autologous graft engineering.

Bone marrow purging in acute lymphoblastic leukemia: biological and clinical features

A group of 56 patients with immunophenotyped acute lymphoblastic leukemia had their bone marrow purged using monoclonal antibody (MAb) and complement. Mononuclear marrow cells were treated with panels of MAb directed against T cells (n = 19), CD10-CALLA (n = 16), and B cells (n = 21), resulting in median specific cell depletions of 96.50, 97.59, and 96.97%, respectively. The resulting CFU-GM recoveries were 60.15, 110.6, and 72.9%. Long-term bone marrow cultures showed normal formation of adherent cell layers in 17 of 23 cases, and failure to form an adherent layer correlated with poor hematological reconstitution. A total of 32 patients (aged 4-40 years) received purged marrow grafts containing a median of 1.32 x 10(7) mononuclear cells/kg and 1.64 x 10(4) CFU-GM/kg; 7 patients required backup marrow. Time to engraftment of 500 granulocytes, 1000 leukocytes, 20,000 platelets, and 50,000 platelets was 37, 38, 39, and 57 days, respectively. A total of 16 patients (50%) remain alive and in complete remission 313-913 days posttransplant (median 565 days); 13 patients (41%) relapsed between 50 and 365 days posttransplant (median 100 days), and 3 patients (9%) died from transplant-associated complications.

Graft-versus-leukemia effect in MHC-compatible and -incompatible allogeneic bone marrow transplantation of radiation-induced, leukemia-bearing mice

Manifestation of graft-versus-leukemia (GVL) effect in MHC-compatible and -incompatible, allogeneic bone marrow transplantation and the roles of T cell subsets contaminated in the donor bone marrow were studied using radiation-induced leukemia-bearing C3H mice maintained under specific-pathogen-free (SPF) condition. The results indicated that BMT from MHC-incompatible allogeneic (B10) donor significantly improved the survival of the treated mice as compared with that from syngeneic (C3H) donor. When donor (B10) bone marrow cells were treated with either anti-Thy 1.2 or anti-Lyt 2.2 antibody plus complement prior to BMT, a beneficial GVL effect was completely abolished. On the other hand, BMT from MHC-compatible allogeneic donors (B10.BR, CBA, AKR) failed to show an improvement in survival. However, intentional enhancement of GVH reaction by preimmunization of B10.BR donor mice with a relatively small number (10(4) approximately 10(5] of C3H spleen cells or by an addition of B10.BR lymph node cells to the donor bone marrow resulted in a significant improvement in survival. The depletion of all T cells completely abrogated the GVL effect, while the depletion of either Lyt 2+ or L3T4+ T cells from donor (B10.BR) bone marrow resulted in only partial, if any, abrogation of GVL effect. The results indicate that GVL effect observed in leukemic mice treated with allogeneic BMT from MHC-compatible (B10.BR) and -incompatible (B10) donors was totally dependent on T cells contaminated in the donor bone marrow, and suggest that the roles of T cell subsets in the induction of GVL effect were different between MHC-compatible (B10.BR) and -incompatible (B10), allogeneic BMT.

Persistence of allospecific helper T cells is required for maintaining autoantibody formation in lupus-like graft-versus-host disease

Induction of a graft-versus-host (GVH) reaction (GVHR) in non-irradiated (C57BL/10ScSn x DBA/2)F1 mice (BDF1) with DBA/2 lymphoid cells leads to chronic GVH disease (GVHD). One of the pathological alterations of this type of GVHD is hyperplasia of host B cells with production of lupus-like autoantibodies. This hyperstimulation of host B cells has previously been demonstrated to be induced by alloreactive donor T helper cells that were also proposed to maintain it. We provide three pieces of experimental evidence in support of this concept. First, treatment of mice with chronic GVHD by injection of monoclonal anti-Thy-1.2 antibodies, performed at week 6 after the injection of C57BL/6 lymphoid cells into (C57BL/6 x C57BL.bm12)F1 mice led to a significant decrease in the titre of anti-nuclear antibodies. Second, CD4+ donor T cells persisted in BDF1 mice with GVHD (GVHF1) for at least 10 weeks after the induction of GVHR; these T cells showed alloreactive helper activity against H-2b MHC determinants of the opposite parent in vitro. Third, T cells of GVHF1 mice, obtained 2 months after the induction of GVHR and transferred into normal secondary recipients, induced signs of chronic GVHD in DBF1 but not in DBA/2 mice. The combined results show that persisting donor T helper cells in GVHF1 mice retain their alloreactivity towards H-2 class II antigens for a long time after the induction of GVHR and they strongly suggest that these T cells are also the driving force behind the production of lupus-like autoantibodies at the late stage of chronic GVHD.

Monoclonal antibody 55 (CD10) and complement used for purging autologous bone marrow in common acute lymphoblastic leukemia

A CD10 monoclonal antibody 55 (McAb55) was intended for purging residual common acute lymphoblastic leukemia antigen (CALLA) positive leukemic cells from autotransplants of common acute lymphoblastic leukemia (C-ALL) patients. It was found that after two rounds of McAb55 and complement treatment, 4-5 logs of CALLA+ cells were removed from bone marrow detected by clonogenic assay. The standardization of separation, purgation and preservation of bone marrow for C-ALL patients' autotransplants was then set as follows: Following the carboxymethyl starch sedimentation and Ficoll-Hypaque gradient separation, the isolated mononuclear cells (MNCs) were treated with McAb55 and complement twice and kept in room temperature for 48-72 hours prior to infusion. This procedure resulted in the removal of more than 99% of CALLA+ cells, recovery of 10-30% MNCs, and leaving the hematopoiesis stem cells intact. After the intensive cytoreductive therapy, 4 patients with C-ALL received the purged autotransplants giving timely recovery of the hematopoietic function. The patients were all remaining in remission status for more than 40-250 days so far.

Monoclonal antibody T-cell-depleted HLA-haploidentical bone marrow transplantation for Wiskott-Aldrich syndrome

Four patients with Wiskott-Aldrich syndrome received bone marrow transplants (BMT) using monoclonal antibody T cell-depleted HLA-haploidentical marrow from a family member donor. The patients did not receive a significantly larger inoculum of mature T cells than other recipients of T cell-depleted marrow transplants. All four patients achieved quick engraftment, and three of the four patients are alive and well today. The three living patients have all had a complete return of normal T-cell and B-cell function. Infectious complications in the surviving patients were minimal; however, all three experienced some degree of graft-versus-host disease (GVHD). Two of these three patients received GVHD prophylaxis. The patient not receiving GVHD prophylaxis experienced severe GVHD and had a difficult posttransplant course. The patient who did not survive was chronically ill before BMT, whereas the other patients were in relatively good health at the time of BMT. Since the majority of individuals with this disease lack a matched bone marrow donor, our results using partially matched donors suggest that a greater number of patients can be successfully treated for Wiskott-Aldrich syndrome and that outcome is related to control of GVHD and state of health before BMT. Marrow transplantation should be offered earlier in the disease course before the onset of major infectious problems.

[Modeling of the "universal" bone marrow using monoclonal antibodies]

The data on the application of monoclonal antibodies (ICO-10) and rabbit complement for working the conditions of allogeneic bone marrow transplantation are presented in the paper. The treatment with monoclonal antibodies and bone marrow complement from BALB/c mice for 2 times prevented the development of transplant versus host reaction and completely protected lethally irradiated (CBA X X C57B1/6)FI mice-recipients from death. Thymus atrophy and the absence of T-cells in the peripheral blood was observed in these mice. The erythrocytes had markers characteristic of BALB/c and (CBA X C57B1/6)FI mice. Mouse splenocytes did not respond to the cells of donors and recipients in mixed lymphocyte culture reaction.

Immunologic reconstitution after haploidentical bone marrow transplantation for immune deficiency disorders: treatment of bone marrow cells with monoclonal antibody CT-2 and complement

Patients with congenital T lymphocyte deficiency disorders received transplants with parental bone marrow depleted of mature T cells by the use of an anti-T cell monoclonal antibody (CT-2) and complement. Our results with 16 consecutive patients (20 transplants) showed rapid engraftment of donor cells; cytoreduction (busulfan, cytosine arabinoside [ara-C], cyclophosphamide) was used in six transplants, and marrow ablation was used in six (ara-C, cyclophosphamide, 1,365-cGy total body irradiation). No patient received prophylactic anti-graft-v-host disease (GVHD) therapy posttransplant, and only one patient developed significant GVHD, which involved the skin, liver, and gastrointestinal tract. Seven others showed some manifestations of GVHD, but these were of minimal clinical significance and required only occasional steroid therapy. Overall, eight patients are alive and well; eight did not survive. Polyclonal immunoglobulin synthesis by donor memory B cells was seen shortly after transplantation, with peak donor-derived serum levels seen approximately 2 months after transplantation. After this initial immunoglobulin synthesis waned, another wave of B cell responses developed. This immunoglobulin response appears to be permanent. T cell functions appeared as soon as 3 weeks after transplantation. This experience in a variety of patients with combined immunodeficiency who received transplants with monoclonal antibody T cell-depleted marrow shows gratifying results with a consistent T and B cell benefit.

Treatment of donor bone marrow with monoclonal anti-T-cell antibody and complement for the prevention of graft-versus-host disease. A prospective, randomized, double-blind trial

The effects of ex-vivo depletion of T lymphocytes from donor bone marrow using a monoclonal anti-T-cell antibody (CT-2) and complement on the outcome of allogeneic bone marrow transplantation was evaluated in a prospective, randomized, double-blind study of 40 patients with leukemia. Patients receiving T-cell-depleted bone marrow had a lower incidence of acute graft-versus-host disease than control patients (3 of 20 compared with 13 of 20; p = 0.004), and mortality due to acute graft-versus-host disease was reduced. Five patients in the T-cell-depletion group developed graft failure; all control patients had sustained engraftment (p less than 0.05). Clinically apparent relapse of leukemia occurred in 7 patients from the T-cell-depletion group and in 2 controls (p, not significant). Cytogenetic evidence of residual leukemia was also detected in the 5 patients with graft failure without overt relapse. Infections and overall survival were similar in the two groups. The effects of T-cell depletion on engraftment and recurrence of leukemia require further evaluation.

Immunomodulators and the complement system

The possible role of immunomodulators in the host-defense mechanism against neoplasm is discussed from the standpoint of the complement system. Serum complement is activated by the majority of immunomodulators in vitro via either the classical or the alternative pathway, and this activation is sometimes observed following systemic administration of immunomodulators. Besides activating the complement, systemic administration of immunomodulators elevates serum complement levels, and in some cases binds complements to tumor cells. Activated serum complement by an immunomodulator induced an accumulation of PMNs in ascites with tumor cell destruction when intraperitoneally injected, indicating that complement-derived chemotactic factors C3a and C5a generated by an immunomodulator had an antitumor effect. This evidence strongly supports the concept that complement system plays an important role in the host-defense mechanism against neoplasm.

Autologous bone marrow transplantation for patients with acute lymphoblastic leukemia in second or subsequent remission: results of bone marrow treated with monoclonal antibodies BA-1, BA-2, and BA-3 plus complement

Autologous bone marrow transplantation (BMT) was utilized as therapy for 23 patients with acute lymphoblastic leukemia (ALL) in second or greater remission. Bone marrow was treated in vitro with a combination of monoclonal antibodies, consisting of BA-1, BA-2, BA-3, and baby rabbit complement (BRC'). All patients were prepared for transplantation with cyclophosphamide and fractionated total body irradiation. Engraftment occurred in all 23 patients. Seven of 23 patients remain relapse-free from six to 32 months (median, 21.4 months) posttransplant. Failures were due to relapse with the exception of one patient who died of infection. This study demonstrates that autologous BMT using in vitro marrow treatment with BA-1, BA-2, BA-3, and BRC' is safe, allows engraftment, and results in prolonged survival for some patients with ALL in second or greater remission.

The immunological basis of tumor rejection: the absolute dependence of the effector arm on sensitized T cells after chemoimmunotherapy of a murine sarcoma

The mechanisms of tumor rejection were investigated by using a therapeutic model system involving treatment of C57BL/6J (B6) mice bearing the syngeneic MCA/76-9 or the unrelated MCA/76-64 sarcomas with cytoxan and tumor-sensitized T lymphocytes. Separated tumor-associated T lymphocytes (TAL) and tumor-associated macrophages (TAM) isolated from the regressing tumors 8 to 10 days after combination therapy expressed relatively specific cytotoxicity in vitro, whereas the unseparated tumor-associated cells (TAC), consisting of a mixture of TAL and TAM, expressed nonspecific cytotoxicity. TAM-mediated cytotoxicity was not dependent on the presence of TAL, as shown by T cell depletion of TAM or TAC cultures with the use of monoclonal anti-Thy-1 or anti-Lyt-2 antibody and complement. In contrast, the nonspecific cytotoxicity was dependent on the presence of T cells. In vivo assays using the Winn test failed to confirm certain aspects of the in vitro data. Without exception, the TAC inhibited tumor growth in an immunologically specific manner, having no effect on the growth of the unrelated B6 sarcoma. T cell depletion completely abrogated in vivo cytotoxicity. Specificity of tumor growth inhibition was confirmed in a bystander experiment in which TAC were mixed with both tumor cell types and were injected into recipient B6 mice. Tumors grew under these conditions, but the tumor that grew consisted only of those tumor cells toward which TAC cytotoxicity was not specifically directed. A bioassay indicated that the specifically immune antitumor effects at the site of regression were initiated between days 3 and 7 after combination therapy. By days 7 and 9, few tumorigenic stem cells could be detected at the tumor site. However, T cell depletion of the TAC isolated on days 8 to 10 resulted in enhanced tumor growth when the depleted TAC were injected into recipient mice. The conclusions reached were that tumor rejection was absolutely dependent on T cell participation at the tumor site, and that if TAM were involved, they required the presence of TAL and did not express nonspecific antitumor cytotoxicity. Indeed, the accelerated tumor growth seen in the absence of TAL suggested the possibility that TAM were growth stimulatory.

Use of SM-1 monoclonal antibody and human complement in selective killing of small cell carcinoma of the lung

SM-1 is a murine monoclonal antibody strongly reactive with a cell membrane antigen of small cell carcinoma (SCC) of the lung but unreactive with the membrane of most other carcinomas and normal tissues including normal bone marrow. We have found that in the presence of human complement, SM-1 antibody is highly cytotoxic to SCC cells. Using three treatments with antibody and complement, more than 99% of SCC cells in culture were lysed, as determined by the chromium release and clonogenic assays. Similar efficiency of SCC cell lysis was observed when one SM-1 antibody treatment was followed by three treatments with human complement. In contrast, there was little antibody-dependent lysis of non-small cell lung cancer cells, other carcinomas, and leukemia cell lines. The amount of chromium released from normal bone marrow cells treated with SM-1 antibody and complement was minimal and was mainly due to the effect of complement alone. Clonogenic assays, including colony-forming unit-granulocytic/monocytic, erythroid burst-forming unit, and colony-forming unit-granulocytic/erythroid/monocytic/megakaryocytic, also showed no significant SM-1 antibody-dependent cytotoxicity on normal bone marrow precursors. Since SM-1 antibody is selectively cytotoxic to SCC cells in the presence of human complement, it is a potentially useful agent for the selective eradication of tumor cell contamination in marrows of patients with metastatic small cell lung cancer and possibly for in vivo serotherapy.

Removal of tumour cells from bone marrow: an evaluation of the available techniques

Autologous bone marrow transplantation has offered a way of increasing the dose of drugs and radiotherapy which can be used to treat patients with malignant disease in an attempt to eradicate tumour. Bone marrow is taken prior to treatment and returned to the patient to 'rescue' haemopoietic function after ablative therapy is completed. Bone marrow removed for autograft may be contaminated with tumour cells at the time of harvest, and it is undesirable to return these to patients even though there are little data available concerning the number of tumour cells necessary to reseed various malignancies. This review considers the various methods available for removing tumour cells from bone marrow destined for autologous transplantation, and evaluates their advantages and disadvantages.

A blood coagulation abnormality in rabbits deficient in the sixth component of complement (C6) and its correction by purified C6

Evidence for the involvement of the sixth component of complement (C6) in normal blood coagulation is provided by the description of a coagulation abnormality in rabbits with a genetic C6 deficiency and by its correction with highly purified preparations of C6. Whole blood clotting time in glass or plastic was prolonged and prothrombin consumption was decreased in blood from the deficient animals. Other parameters of blood coagulation were normal, including prothrombin time, partial thromboplastin time, specific clotting factor activities, platelet factor III function, platelet count, and bleeding time. Clotting time and prothrombin consumption became normal when physiologic amounts of highly purified C6 were added to the deficient blood. Partial consumption of C6 hemolytic activity, with a time course similar to the consumption of prothrombin, was demonstrated during the clotting of normal human blood.