Phase I study of safety and pharmacokinetics of the anti-MUC16 antibody-drug conjugate DMUC5754A in patients with platinum-resistant ovarian cancer or unresectable pancreatic cancer.

BACKGROUND: MUC16 is a tumor-specific antigen overexpressed in ovarian (OC) and pancreatic (PC) cancers. The antibody-drug conjugate (ADC), DMUC5754A, contains the humanized anti-MUC16 monoclonal antibody conjugated to the microtubule-disrupting agent, monomethyl auristatin E (MMAE). PATIENTS AND METHODS: This phase I study evaluated safety, pharmacokinetics (PK), and pharmacodynamics of DMUC5754A given every 3 weeks (Q3W, 0.3-3.2 mg/kg) or weekly (Q1W, 0.8-1.6 mg/kg) to patients with advanced recurrent platinum-resistant OC or unresectable PC. Biomarker studies were also undertaken. RESULTS: Patients (66 OC, 11 PC) were treated with DMUC5754A (54 Q3W, 23 Q1W). Common related adverse events (AEs) in >20% of patients (all grades) over all dose levels were fatigue, peripheral neuropathy, nausea, decreased appetite, vomiting, diarrhea, alopecia, and pyrexia in Q3W patents, and nausea, vomiting, anemia, fatigue, neutropenia, alopecia, decreased appetite, diarrhea, and hypomagnesemia in Q1W patients. Grade ≥3-related AE in ≥5% of patients included neutropenia (9%) and fatigue (7%) in Q3W patients, and neutropenia (17%), diarrhea (9%), and hyponatremia (9%) in Q1W patients. Plasma antibody-conjugated MMAE (acMMAE) and serum total antibody exhibited non-linear PK across tested doses. Minimal accumulation of acMMAE, total antibody, or unconjugated MMAE was observed. Confirmed responses (1 CR, 6 PRs) occurred in OC patients whose tumors were MUC16-positive by IHC (2+ or 3+). Two OC patients had unconfirmed PRs; six OC patients had stable disease lasting >6 months. For CA125, a cut-off of ≥70% reduction was more suitable for monitoring treatment response due to the binding and clearance of serum CA125 by MUC16 ADC. We identified circulating HE4 as a potential novel surrogate biomarker for monitoring treatment response of MUC16 ADC and other anti-MUC16 therapies in OC. CONCLUSIONS: DMUC5754A has an acceptable safety profile and evidence of anti-tumor activity in patients with MUC16-expressing tumors. Objective responses were only observed in MUC16-high patients, although prospective validation is required. CLINICAL TRIAL NUMBER: NCT01335958.

Experimental histoplasmosis in mice treated with anti-murine interferon-gamma antibody and in interferon-gamma gene knockout mice.

Histoplasma capsulatum is an important fungal pathogen in immunocompromised hosts, including AIDS patients. Experimental evidence suggests interferon-gamma (IFN) plays a role in host defense against H. capsulatum. In these studies we sought to demonstrate the importance of IFN in innate resistance to systemic histoplasmosis. The possible exacerbation of infection in BALB/c mice was assessed by administering 200 microg of hamster anti-IFN antibody prior to infection with H. capsulatum (2 x 10(6) yeasts, i.v.) and by comparing the severity of infection between BALB/c IFN gene knockout mice (GKO) and congenic control animals. In two separate studies, we found that anti-IFN treatment caused a dramatic loss of resistance to lethal infection and resulted in earlier mortality of IFN-depleted animals compared with normal IgG or no treatment (P<0.001). GKO mice were significantly (P<0.001) more susceptible to lethal infection than were control animals, and histological studies corroborated this. These studies clearly demonstrate that IFN is a vital part of the host's innate resistance to systemic infection with H. capsulatum and provide an additional rationale for studying IFN as an immunomodulatory therapeutic for the treatment of this disease.

Ischemic stroke injury is reduced in mice lacking a functional NADPH oxidase.

BACKGROUND AND PURPOSE: Free radicals account for a significant proportion of the brain damage that occurs during ischemic stroke. Using mutant mice (X-CGD) with a dysfunctional phagocytic NADPH oxidase, we investigated the role of this superoxide-generating enzyme as a mediator of the reperfusion injury in a mouse model of middle cerebral artery occlusion. METHODS: Transient (2 hour) middle cerebral artery occlusion was performed in X-CGD or wild-type litter mates (8- to 10-week-old). After 22 hours of reperfusion, brains were harvested and infarct volume delineated using 2,3,5-triphenyl-tetrazolium chloride. To elucidate the origin of the damaging NADPH oxidase, transient ischemia was also performed in X-CGD or wild-type mice transplanted with wild-type C57 B1/6J or X-CGD bone marrow, respectively. RESULTS: The infarct volume induced by transient ischemia was significantly less in X-CGD mice (29.1 +/- 5.6 mm3; n = 13) than wild-type littermates (54.0 +/- 10.6 mm3; n = 10; P < .05). The elimination of a functional NADPH oxidase from either the circulation or the central nervous system, by performing the appropriate bone marrow transplant experiments, did not reduce the infarct size induced by transient ischemia. This suggests that in order to confer protection against transient ischemia and reperfusion, a putative neuronal and circulating NADPH oxidase need to be inactivated. CONCLUSIONS: Brain injury was reduced in mice lacking a functional NADPH oxidase in both the central nervous system and peripheral leukocytes, suggesting a pivotal role for the NADPH oxidase in the pathogenesis of ischemia-reperfusion injury in the brain.

Expression cloning of cardiotrophin 1, a cytokine that induces cardiac myocyte hypertrophy.

Heart failure continues to be a leading cause of mortality worldwide. A hallmark of this disease is dilated cardiac hypertrophy, which is accompanied by a reactivation of genes expressed in fetal heart development. Reasoning that fetal or embryonic growth factors may mediate the onset of cardiac hypertrophy, we have coupled expression cloning with an embryonic stem cell-based model of cardiogenesis to isolate a 21.5-kDa protein, cardiotrophin 1, that potently induces cardiac myocyte hypertrophy in vitro. Amino acid similarity data indicate that cardiotrophin 1 is a member of the leukemia inhibitory factor/ciliary neurotrophic factor/oncostatin M/interleukin 6/interleukin 11 family of cytokines. Several members of this family that are known to signal through the transmembrane protein gp130 stimulate cardiac myocyte hypertrophy, like cardiotrophin 1, suggesting that the gp130 signaling pathway may play a role in cardiac hypertrophy. A 1.4-kb cardiotrophin 1 mRNA is expressed in the heart and several other mouse tissues.

Stimulation of megakaryocytopoiesis and thrombopoiesis by the c-Mpl ligand.

Physiological platelet synthesis is thought to require the humoral activities of meg-CSF and thrombopoietin, which respectively promote proliferation and maturation of megakaryocytic cells. A meg-CSF/thrombopoietin-like protein that is present in plasma of irradiated pigs has been purified and cloned. This protein binds to and activates the c-mpl protein, a member of the cytokine receptor superfamily. The isolated Mpl ligand shares homology with erythropoietin and stimulates both megakaryocytopoiesis and thrombopoiesis.

A receptor for the malarial parasite Plasmodium vivax: the erythrocyte chemokine receptor.

Plasmodium vivax and P. falciparum are the major causes of human malaria, except in sub-Saharan Africa where people lack the Duffy blood group antigen, the erythrocyte receptor for P. vivax. Duffy negative human erythrocytes are resistant to invasion by P. vivax and the related monkey malaria, P. knowlesi. Several lines of evidence in the present study indicate that the Duffy blood group antigen is the erythrocyte receptor for the chemokines interleukin-8 (IL-8) and melanoma growth stimulatory activity (MGSA). First, IL-8 binds minimally to Duffy negative erythrocytes. Second, a monoclonal antibody to the Duffy blood group antigen blocked binding of IL-8 and other chemokines to Duffy positive erythrocytes. Third, both MGSA and IL-8 blocked the binding of the parasite ligand and the invasion of human erythrocytes by P. knowlesi, suggesting the possibility of receptor blockade for anti-malarial therapy.

The human erythrocyte inflammatory peptide (chemokine) receptor. Biochemical characterization, solubilization, and development of a binding assay for the soluble receptor.

In addition to the two human interleukin-8 (IL-8) receptors that have been cloned, IL-8RA and IL-8RB, we recently described a binding protein in human erythrocytes that binds IL-8 and monocyte chemotactic peptide-1 (MCP-1), which we have termed the chemokine (CK) receptor. This communication describes the biochemical characterization, detergent solubilization, and development of a solubilized receptor binding assay for the erythrocyte CK receptor. Competitive 125I-IL-8 binding studies in cells transfected with IL-8RA and IL-8RB revealed that only IL-8 and MGSA were able to displace the radiolabeled IL-8 from these cells. In contrast, a whole array of chemokines were able to cross-compete with 125I-IL-8 for binding to the CK receptor in erythrocyte ghosts. Scatchard analysis of 125I-IL-8 binding to erythrocyte membranes and to dodecyl beta-maltoside solubilized CK receptors revealed a single class of high affinity binding sites in both cases with KD values of 9.5 nM +/- 3.6 and 15.4 nM +/- 5.0, respectively. Chemical cross-linking studies with erythrocyte membranes and with solubilized CK receptors indicated that the CK receptor has a lower molecular mass than the cloned IL-8 receptors (39 kDa compared to 57-69 kDa). Treatment of the cross-linked 47-kDA protein with N-glycanase reduced its molecular mass to 42 kDa.

Identification of a promiscuous inflammatory peptide receptor on the surface of red blood cells.

Erythrocytes have long been appreciated as transporters and exchangers of O2 and CO2 between the lungs and the tissues. Here we examine the role of erythrocytes as potential mediators of inflammatory processes by assessing their ability to bind to a number of inflammatory peptides of the chemokine (for chemoattractant cytokine) superfamily. Radiolabeled chemokines of either the C-X-C (IL-8, MGSA/gro, NAP-2) or C-C (RANTES, MCP-1) class bind reversibly to red cell surface receptors numbering 1000-9000 sites/cell with a Kd of approximately 5 nM. In contrast to what is seen for chemokine binding to target inflammatory cells, chemokines of either class displace heterologous chemokines, indicating that the proteins are competing for a promiscuous receptor. Chemical cross-linking with radiolabeled chemokines reveals a 30-38-kilodalton protein on the red cell surface, and cross-linking is inhibited in the presence of heterologous unlabeled chemokines. These data show that red blood cells possess a multispecific receptor for the newly identified chemokine superfamily of inflammatory cytokines, and thus the red cell may play a novel role as a regulator of inflammatory processes.

Red blood cells are a sink for interleukin 8, a leukocyte chemotaxin.

IL-8 (also known as neutrophil-activating peptide 1) is recognized as a potent effector of neutrophil functions. Several different cell types that contact blood, namely T lymphocytes, monocytes, and endothelial cells, secrete this polypeptide following stimulation by cytokines, or lipopolysaccharide. Here we show that when IL-8 is added to blood it rapidly partitions from the plasma fluid to the blood cells and that erythrocytes account for the vast majority of this binding. Analysis of 125I-IL-8 binding [( ala-IL-8]77 form) to human red cells indicates a single, 5 nM Kd affinity class of binding sites, present at approximately 2,000 per red cell representing approximately 15 nmol of red cell IL-8 binding sites per liter of blood. These sites are protease sensitive. Their binding of IL-8 is rapidly reversible and does not result in receptor internalization, although bound IL-8 is resistant to extraction by pH 3 buffer at 5 degrees C. 125I-IL-8 binding to red cells was not inhibited by epidermal growth factor or interleukin 1, but was inhibited by monocyte chemotactic peptide-1, which is not a neutrophil chemotaxin, but is a member of the same family of polypeptides as IL-8. FACS analysis of IL-8-mediated mobilization of Ca2+ in neutrophils indicates that the IL-8 bound to red cells is incapable of stimulating neutrophils. Thus, red cell absorption of IL-8 may function to limit stimulation of leukocytes by IL-8 released into blood.

Endothelial and leukocyte forms of IL-8. Conversion by thrombin and interactions with neutrophils.

We have recently shown that endothelial cell-derived IL-8 inhibits neutrophil adhesion to IL1-beta-activated human umbilical vein endothelial cell monolayers. IL-8 secreted by T lymphocytes or monocytes has been characterized as a promoter of neutrophil degranulation and chemotaxis. The IL-8 isolated from each of these cell types is a mixture of two IL-8 polypeptides, one consisting of 72 amino acids (herein called [ser-IL-8]72) and the other 77 amino acids (an N-terminal extended form herein called [ala-IL-8]77). IL-8 derived from T lymphocytes and monocytes is predominantly [ser-IL-8]72, whereas endothelial-derived IL-8 is highly enriched (greater than 80%) in [ala-IL-8]77. We address the relationship and activities of these two forms of IL-8 using recombinant proteins expressed by both mammalian cells and Escherichia coli. Thrombin was found to efficiently convert [ala-IL-8]77 to [ser-IL-8]72. In contrast, urokinase and tissue-type plasminogen activator were unable to cleave [ala-IL-8]77, and trypsin generated multiple IL-8 cleavage fragments. In competitive binding assays using 125I[ala-IL-8]77 neutrophils exhibited a twofold preference for [ser-IL-8]72 over [ala-IL-8]77. Both forms of IL-8 inhibited neutrophil adhesion to IL-1-beta-activated HUVEC monolayers by up to 90%. However, [ser-IL-8]72 was approximately 10-fold more potent than [ala-IL-8]77 in these assays (ED50 approximately 0.3 nM for [ser-IL-8]72 vs approximately 3 nM for [ala-IL-8]77. Both forms of IL-8 promoted degranulation of cytochalasin B-treated neutrophils [[ser-IL-8]72 (ED50 greater than 10 nM) was two- to three-fold more potent than [ala-IL-8]77], although in this regard they were less active than FMLP. Our data suggest that [ala-IL-8]77 and [ser-IL-8]72 have qualitatively similar and potentially complex biological activities, and that full activation of IL-8 requires cleavage to the [ser-IL-8]72 form. In the case of inflamed endothelial cells this activation could be mediated by thrombin generated in the procoagulant environment associated with these cells.

Interaction of wild-type and catalytically inactive mutant forms of tissue-type plasminogen activator with human umbilical vein endothelial cell monolayers.

Several groups have demonstrated that radioiodinated tissue-type plasminogen activator (t-PA) binds to saturable sites on human umbilical vein endothelial cells (HUVECs) in culture (Hajjar, K. A., Hamel, N. M., Harpel, P. C., and Nachman, R. L. (1987) J. Clin. Invest. 80, 1712-1719; Beebe, D. P. (1987) Thromb. Res. 46, 241-254; Barnathan, E. S., Kuo, A., van der Keyl, H., McCrae, K. R., Larsen, G. L., and Cines, D. B. (1988) J. Biol. Chem. 263, 7792-7799). Here we report that most of the specific binding of 125I-t-PA to our HUVEC cultures is accounted for by binding to (i) plasminogen activator inhibitor type 1 (PAI-1), a t-PA inhibitor produced in abundance by HUVECs; and (ii) specific binding sites present on the plastic culture surface. The contribution of the sites on plastic can be eliminated by taking several precautions. Then, most or all of the specifically bound 125I-t-PA is present in a sodium dodecyl sulfate-stable 110-kDa 125I-t-PA.PAI-1 complex. Interestingly, a radioiodinated mutant form of t-PA, S478A, which is catalytically inactive and therefore unable to form the covalent complex with PAI-1, still binds to HUVECs. In fact, this ligand binds to HUVECs in 10-30-fold greater amounts than does wild-type 125I-t-PA (resulting in greater than 1 x 10(7) S478A 125I-t-PA molecules bound/cell at 12 nM ligand concentration). In contrast, diisopropyl fluorophosphate-treated t-PA binds to HUVECs in much smaller amounts than does wild-type t-PA. Several findings suggest that PAI-1 is a major binding site for S478A t-PA. The vast amount of binding observed with S478A t-PA, compared with wild-type t-PA, may be accounted for by an observed large scale release of wild-type 125I-t-PA.PAI-1 complexes from the solid phase (cells or extracellular matrix) into the culture medium. Immunoprecipitation experiments demonstrate that, in contrast to wild-type t-PA, S478A t-PA does not extract [35S]methionine-PAI antigen from metabolically labeled extracellular matrix. It is proposed that t-PA releases PAI-1 from the solid phase when it forms the irreversible covalent complex with the inhibitor, a process that does not occur with the catalytically inactive mutant form of t-PA.