A Bispecific Molecule Targeting CD40 and Tumor Antigen Mesothelin Enhances Tumor-Specific Immunity

Agonistic CD40 monoclonal antibodies (mAb) have demonstrated some clinical activity, but with dose-limiting toxicity. To reduce systemic toxicity, we developed a bispecific molecule that was maximally active in the presence of a tumor antigen and had limited activity in the absence of the tumor antigen. LB-1 is a bispecific molecule containing single-chain Fv domains targeting mouse CD40 and the tumor antigen mesothelin. LB-1 exhibited enhanced activity upon binding to cell-surface mesothelin but was less potent in the absence of mesothelin binding. In a mouse model implanted with syngeneic 4T1 tumors expressing cell-surface mesothelin, LB-1 demonstrated comparable antitumor activity as an agonistic CD40 mAb but did not cause elevation of serum cytokines and liver enzymes, as was observed in anti-CD40-treated mice. The results from our study of LB-1 were used to develop a human cross-reactive bispecific molecule (ABBV-428) that targeted human CD40 and mesothelin. ABBV-428 demonstrated enhanced activation of antigen-presenting cells and T cells upon binding to cell-surface mesothelin, and inhibition of cultured or implanted PC3 tumor cell growth after immune activation. Although expression of cell-surface mesothelin is necessary, the bispecific molecules induced immune-mediated antitumor activity against both mesothelin⁺ and mesothelin^- tumor cells. ABBV-428 represents a class of bispecific molecules with conditional activity dependent on the binding of a tumor-specific antigen, and such activity could potentially maximize antitumor potency while limiting systemic toxicity in clinical studies.

Abstract C18: A phase I study of enavatuzumab (PDL192, ABT-361), a first-in-class human monoclonal antibody targeting TWEAK (tumor necrosis factor-like inducer of apoptosis) receptor, in patients (Pts) with advanced solid tumors

Background: TWEAK receptor (TweakR, TNFRSF12A, CD266) is a member of the TNF receptor superfamily and is expressed on a range of solid tumors. Enavatuzumab is a humanized IgG1 antibody to TweakR that exhibits anti-tumor activity in preclinical models through two mechanisms: direct signaling through TweakR and antibody-dependent cellular cytotoxicity.

Methods: This phase I, multicenter study was designed to determine the maximum tolerated dose (MTD) and to evaluate the safety and pharmacokinetic (PK) profiles of enavatuzumab, given intravenously over 60 minutes on days 1 and 15 of each 28-day cycle. Pts with advanced solid tumors; ECOG ≤1; adequate hematologic, renal, and hepatic function; no brain metastasis; no history of cirrhosis or pancreatitis; no recent history of acute cholecystitis; and not on immunosuppressive drugs were enrolled. Cohorts of 3–6 pts were treated at escalating dose levels of enavatuzumab ranging from 0.1 mg/kg to 1.5 mg/kg. Dose limiting toxicity (DLT) was defined as grade (G) 3 AST or ALT lasting >14 days or associated with clinical hepatitis and/or bilirubin ≥G2; G3 amylase or lipase lasting >14 days; ≥G3 bilirubin; any G4 AST, ALT, amylase, or lipase; acute pancreatitis; ≥G3 hematologic and non-hematologic toxicities; G4 cytokine release syndrome (CRS) or G3 CRS despite premedication. MTD was defined as the highest dose level with 0/3 or ≤1 of 6 pts experiencing a first-cycle DLT. PK sampling was performed on cycle 1 day 1 (C1D1), C1D2, C1D8, Day 15 of all cycles, C1D16, C2D1, and C3D1. Response was assessed by RECIST every 8 weeks.

Results: Thirty pts [12 male, 18 female; median age 64.5 (range 36–82)] were enrolled at 6 dose levels: 0.1, 0.3, 0.5, 0.7, 1.0, and 1.5 mg/kg. Tumor types included colorectal (15); pancreas (4); ovarian (4); and tongue, cervical, prostate, endometrial, breast, hepatocellular, and thyroid (1 each). Sixteen pts had liver metastases. DLTs included G4 lipase and G3 bilirubin in 1 of 6 pts at the 1.0 mg/kg level and G4 lipase and G4 amylase in 1 pt at the 1.5 mg/kg level. Grade 3/4 toxicities in ≥5% of subjects included fatigue, pneumonia, hyponatremia, hypoxia, dyspnea, and elevated AST, ALT, GGT, lipase, and amylase. There was no apparent correlation of liver or pancreatic enzyme elevation with tumor type or presence of liver metastases. Of the disease evaluable pts, 11 had disease progression as their best response and 2 had stable disease (2 and 4 month duration). Enavatuzumab followed a two-compartment linear PK model. The estimated clearance was 23–33 mL/hr and elimination half-life was 7–18 days. The mean Cmax after the first dose was 2.0 mcg/mL and 28.1 mcg/mL for the 0.1 mg/kg and 1.0 mg/kg cohorts, respectively. Mean Css was reached following the second dose and was within the target efficacious peak and trough levels for the 1.0 mg/kg cohort.

Conclusions: The MTD for this first-in-class drug was reached at 1.0 mg/kg. Six of 7 pts at 1.0 mg/kg and 1 of 1 pts at 1.5 mg/kg had ≥G3 liver and/or pancreatic enzyme elevations; therefore higher doses are not being tested. The mechanisms of liver and pancreatic enzyme toxicity are currently being investigated and preclinical studies are ongoing to assess potential combination strategies.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr C18.

Abstract 1770: Enavatuzumab (PDL192), a humanized monoclonal antibody to TweakR, displays broad anticancer activity which is dependent on NFκB signaling

TWEAK (TNFSF12) is a multifunctional cytokine that binds to the cell surface receptor TweakR (Fn14, TNFRSR12A). TweakR is overexpressed in many solid tumor types, including cancers of breast, pancreatic, and ovarian origin. The initial functional description of TWEAK described it as a weak inducer of apoptosis in certain cancer cell lines. TWEAK is also known to function in other diverse biological processes such as inflammation, tissue repair, angiogenesis, cell migration, and growth inhibition. The growth inhibitory activity of TWEAK observed in some cancer cell lines and the overexpression of its receptor in cancer led to investigation of targeting TweakR as a therapeutic modality. Enavatuzumab (PDL192), a humanized IgG1 mAb to TweakR, exhibits some of the same functional activities of TWEAK and is currently in clinical investigation for the treatment of solid tumors due to its significant in vitro and in vivo growth inhibitory activity in models of multiple solid tumor types.

The purpose of the current study was to provide insight into the mechanism of action of enavatuzumab and to further our understanding of the biology of TweakR in tumor cell lines. A panel of 106 cancer cell lines was tested for the ability of enavatuzumab to inhibit in vitro cell growth to identify characteristics of response. Of the 106 cell lines tested, 33 cell lines had >25% growth inhibition in response to the drug. Using luciferase transcriptional reporter constructs, it was revealed that the NFκB pathway was activated in response to enavatuzumab treatment in responder cells. Both classical (p50/p65) and non-classical NFκB (p52/RelB) pathways were subsequently shown to be induced by enavatuzumab treatment using Western blot and functional ELISA in responder cell lines. Using Affymetrix™ microarrays, we observed that cell lines sensitive to enavatuzumab had a higher number of transcriptional changes compared with resistant cells and included many genes known to be regulated by NFκB. To confirm a role for NFκB in enavatuzumab-mediated signaling, we inhibited NFκB pathway induction using siRNAs to the individual NFκB subunits p50, p65, p52, and RelB as well as the upstream kinases IKKα and IKKβ. The siRNAs were able to block enavatuzumab's growth inhibitory activity in multiple sensitive cell lines. Further confirmation of the importance of NFκB was obtained using a small molecule inhibitor of IKKα/β (IKK16) which significantly reduced the drug-induced growth inhibition. The finding that NFκB drives the growth inhibitory activity of enavatuzumab is a compelling function for a family of transcription factors that are more frequently associated with cancer growth and survival than inhibition of cell proliferation.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1770. doi:10.1158/1538-7445.AM2011-1770

Abstract 1772: PDL192, a humanized anti-Tweak receptor monoclonal antibody, mediates antitumor effects in primary human breast carcinoma xenografts

Background: PDL192 is a humanized IgG1 monoclonal antibody that binds the human TWEAK receptor (TweakR). TweakR, a member of the TNFR (Tumor Necrosis Factor Receptor) superfamily, is overexpressed in several human cancers including breast cancer (BC). In BC, it may also play a role in the invasive and metastatic potential of the disease (Willis et al, Mol Cancer Res 2008). In TweakR-expressing cancer cell lines or mouse xenograft models, PDL192 has a potent antitumor effect (Culp et al., CCR 2010). All these data therefore suggest that anti-TweakR targeting could be a promising new therapeutic approach for human BC patients.

Material and methods: TweakR expression was assessed by IHC (immunohistochemistry) on 3 Tissue-Micro-Array (TMA) banks of BC samples (basal-like, ERBB2, and luminal A/B), and 25 primary human BC xenografts (HBCx). The cut-off of positivity was defined as at least 25% cells with membraneous or cytoplasmic staining or by a combined score of percentage of positive staining cells x intensity > 50. The in vivo antitumor effect of PDL192 was then assessed on 7 TweakR-positive models (10 mg/kg thrice a week for 3 weeks by intraperitoneal route) in which one in combination with chemotherapy as maintenance therapy, as previsouly reported (Marangoni et al., BJC 2009).

Results: TMA analyses showed that TweakR was expressed in 16/37 basal like BC (43%), 23/37 ERBB2-positive BC (62%), and 38/71 luminal BC (54%). A high TweakR expression was correlated with double estrogen receptor- and Her2-positive tumors. Moreover, 13/25 xenografts have been found to be TweakR-positive (52%). Nine human BC models have been treated with PDL192, with 4 models (44%) showing a tumor growth inhibition (TGI) ranging between 59% and 91%. No correlation has been observed between TweakR expression and in vivo TGI. Moreover, when PDL192 was administered in complete remission after chemotherapy (doxorubicin + cyclophosphamide), we observed a highly significant delay of relapse greater than 2 months.

Conclusions: TweakR is expressed in 77/145 human BC samples (53%). In in vivo experiments, PDL192 showed potent TGI in 4/9 models, and significantly delayed tumor relapses after chemotherapy-induced complete remission. All these data therefore support the use of anti-TWEAK receptor monoclonal antibodies in the treatment of TweakR-positive BC patients.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1772. doi:10.1158/1538-7445.AM2011-1772

Developmental gonadal expression of the transcription factor SET and its target gene, P450c17 (17alpha-hydroxylase/c17,20 lyase)

Cytochrome P450c17 catalyzes the 17alpha-hydroxylase/17,20 lyase activity needed for sex steroid synthesis. We recently characterized the nuclear phosphoprotein SET as a novel transcriptional regulator that binds to the -447/-399 region of the rat P450c17 gene, along with the transcription factors COUP-TF II, NGF-IB, and SF-1. Gel shift studies localized SET binding to nucleotides -410/-402. We have shown that SET activates transcription of the rat P450c17 gene in neuronal precursor cells and now show that it also activates transcription from the -418/-399 region of the rat P450c17 gene in mouse Leydig MA-10 cells. Studying the ontogenic expression of SET and P450c17 in the rodent gonad, we found that SET expression preceded P450c17 expression in the embryonic genital ridge, suggesting that SET may be important for initiating P450c17 expression in this region. Expression of SET also preceded P450c17 expression in the testis and ovary, and its expression was much greater during embryogenesis than in the adult gonad. In the adult rat testis, P450c17 was expressed only in Leydig cells, while SET was expressed in Leydig cells and in spermatocytes. In the adult rat ovary, P450c17 was expressed only in theca cells, while SET was expressed in theca cells and also in oocytes. Because SET is expressed early in development in the genital ridge and in the testis and ovary, and because SET has many functions in addition to its activity as a transcription factor, we determined whether SET acts a transcription factor in oocytes. The SET protein was detected by Western blots in Xenopus oocytes from stages II through VI and in mature oocytes. Using extracts of Xenopus oocytes in gel shift assays, we detected a protein that bound to the -418/-399 region of the rat P450c17 gene, to which SET binds. Nuclear injection of either a -418/-399TK32LUC wildtype reporter construct or a construct containing a mutant SET site into Xenopus oocytes from stages III through VI resulted in activation of luciferase activity with the wildtype but not the mutant construct in all stages. These data suggest that Xenopus SET is able to bind to specific DNA sequences to activate transcription at all stages of Xenopus oogenesis. These data indicate that SET is an evolutionarily conserved transcription factor that participates in the early ontogenesis of the gonadal system, regulates P450c17 gene transcription in Leydig cells, and may also activate other genes expressed in immature oocytes, thus playing a role in oocyte development.

Integration and germ-line transmission of a pseudotyped retroviral vector in zebrafish

The zebrafish is rapidly becoming a popular model system for the study of vertebrate development because it is ideal for both embryological studies and genetic analysis. To determine if a retroviral vector pseudotyped with the envelope glycoprotein of the vesicular stomatitis virus could infect zebrafish embryos, and in particular, the cells destined to become the germ line, a pseudotyped virus was injected into blastula-stage zebrafish embryos. Fifty-one embryos were allowed to develop and eight transmitted proviral DNA to their progeny. Founders were mosaic, but as expected, transgenic F1's transmitted proviral DNA in a Mendelian fashion to the F2 progeny. Transgenic F1 fish inherited a single integrated provirus, and a single founder could transmit more than one viral integration to its progeny. These results demonstrate that this pantropic pseudotyped vector, originally developed for human gene therapy, will make the use of retroviral vectors in zebrafish possible.

High-frequency germ-line transmission of plasmid DNA sequences injected into fertilized zebrafish eggs

With the goal of developing techniques for DNA insertional mutagenesis in zebrafish, we established procedures for rapidly obtaining and injecting large numbers of fertilized eggs. Using either of two plasmid constructs, we injected uncut DNA into fertilized eggs at the one- or two-cell stage. Fish hatched from injected eggs were raised to sexual maturity, and the frequency of transgenic founder fish was determined by pair-mating the fish and testing DNA extracted from pools of their 16-hr-old offspring by the polymerase chain reaction (PCR) and then Southern analysis. Eggs injected with one of two different plasmids yielded no transgenic fish, but 7-25% (19 of 115 overall) of the eggs injected with the other plasmid transmitted the injected sequences to their offspring (F1). Of seven lines studied further, all were able to pass the foreign DNA sequences to the next (F2) generation. Inheritance in the F2 generation was Mendelian in the five lines tested. PCR and Southern analysis indicated that the plasmid sequences were present in multiple copies, probably tandemly arranged. Two founder fish carried more than one independent integration of the plasmid sequences. The line studied in more detail was a mosaic carrying two independently segregating copies of the transgene in one germ cell and a third copy in another germ-line precursor cell. The ability to obtain and inject large numbers of zebrafish eggs combined with a high frequency of germ-line integration may be steps toward the goal of being able to perform insertional mutagenesis with this organism.

Characterization of endogenous and recombinant proviral elements of a highly tumorigenic AKR cell line

As an approach to evaluating the contribution of classes of endogenous viral sequences to leukemogenesis, a genomic library was prepared from the highly tumorigenic AKR SL12.3 cell line and screened for env-containing proviruses. An extensive battery of virus-derived probes and specific oligonucleotide probes were used to segregate 83 positive clones into related groups. The nonecotropic endogenous retroviruses were identified as members of the polytropic, modified polytropic, or xenotropic groups. At least three unique xenotropic proviruses were detected that differed from the published xenotropic sequence within a variable region of the 5' portion of env. Changes among the xenotropic proviruses included relative insertions and/or deletions that maintain an open reading frame and hence the potential to encode viable envelope gene products. Several recombinant viruses were also detected. Recombination was not random and primarily involved the formation of mink cell focus-inducing class I retroviruses via recombination between polytropic elements and ecotropic virus. One other recombinant was detected which contained ecotropic virus sequences in the 5' region encoding p15 of an otherwise xenotropic provirus. An interesting observation was the finding that certain clones contained more than one provirus within the average 20-kb cloned insert. This would not be expected if integration were totally random. The de novo recombinant proviruses identified here provide a series of potential candidates to be evaluated for their contribution to the tumorigencity of the SL12.3 cell line.

Lateral lumbar spine roentgenograms: potential role in complications of lumbar disc surgery

Penetration into the abdominal cavity with injury to visceral, vascular, or neural structures is a potentially life-threatening complication of lumbar disc exploration. In this report, we used reconstructed computed tomographic measurements of the L3-L4, L4-L5, and L5-S1 intervertebral discs to show that lateral spine roentgenograms contain an unavoidable magnification error that makes accurate measurement of minimal depth to penetration impossible. This magnification error may mislead the unwary surgeon into an overestimation of actual disc size. Moreover, the "safe distances" that have been published for the avoidance of penetration at the L3-L4, L4-L5, and L5-S1 intervertebral levels would have been excessive for 22.2%, 19.4%, and 8.3%, respectively, of the 26 patients in our study.

Breaststroker's knee: pathology, etiology, and treatment

Twenty-three breaststroke swimmers (ranging in age from 6 to 30 years old) with painful knees were examined. Underwater movies of these swimmers were taken. Eighteen swimmers had tenderness under the medial facet of the patella and over the medial femoral intercondylar ridge. Five of these 18 swimmers also had tenderness along the tibial collateral ligament. Five swimmers had tenderness just along the tibial collateral ligament. The onset of knee pain usually occurred within 3 years of the swimmers' beginning the breaststroke. Initially, the knees were only symptomatic when the swimmers performed the whipkick. As the swimmer continued the breaststroke, in spite of discomfort, the knees became symptomatic during other athletic and nonathletic activity. Breaststroke who had been using the whipkick for more than 8 years had clinical evidence of patellofemoral osteoarthritis. The site of pain in the knee was related to the way in which the whipkick was performed. Breaststroke without knee pain used a whipkick with characteristics that were consistently different than those of the symptomatic swimmers. Treatment of breaststroke's knee should be directed toward correcting the swimmer's whipkick. This approach is most likely to be successful if applied as soon as the swimmer becomes symptomatic.

Nursing care of the patient with spinal cord injury

The rehabilitation process must begin at the onset of illness and include not only a cure for the immediate disorders but methods of preventing further disability, the general management of convalescence, and the ultimate return of the individual to his maximum health and efficiency. As a member of the rehabilitation team the nurse must recognize the patient as a human being and emotionally accept him, maintain good interpersonal relations with other team members, know what resources are available, and help to provide continuity of care when the patient is discharged. She must counsel and guide the patient and family, know and apply good general nursing care, and understand the emotional factors in long-term care. When deformities and other complications are prevented and the patient keeps up his strength through early activities, the confinement will be shorter, the cost will be less, and the patient will return more quickly to independence.