AB1, a novel protein targeting TP53 mutated GI tumors

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Background: The tumor suppressor gene TP53 is one of the most frequently deleted or mutated genes in gastrointestinal cancers. Normal p53 regulates several important proteins that control cell cycle, cell death, DNA damage/repair, stemness, differentiation and other key cellular functions. If the TP53 gene is damaged, tumor suppression is severely compromised. On the other hand, and downstream of p53, p21 a potent cyclin-dependent kinase inhibitor (CKI) protein binds and inhibitsthe activity of cyclin - CDK2, - CDK1, and - CDK4/6, thus functioning as a regulator ofcell cycle progression at G 1 and S phase. It can act as de facto p53 repair/ replacement mechanism. We have thus hypothesised that, if we were able to deliver wild type p21 into all p53 mutated cancer cells, it would have a possible therapeutic effect. Methods: We have constructed recombinantly a new fusion protein, named AB1, composed of a cell penetrating protein (antennapedia) ANTP and wild type p21 and tested it in in vitro and in vivo preclinical models prior to clinical studies. AB1 could also be constructed semi-synthetically by conjugating recombinant ANTP chemically to p21 protein. Results: AB1 penetrated and killed p53 mutated cancer cells but did not kill cells that did not have p53 mutations AB1 penetrated but did not kill p53- or p21- wild-type cells. AB1 was not immunogenic in normal New Zealand White rabbits. AB1 was more cytotoxic when administered with conventionally-used chemotherapeutic agents. Conclusions: We have generated a selectively cytotoxic fusion protein against p53 mutated GI cancers which is effective when used as a single agent but more so when used in combination with chemotherapy. The phaseI/II clinical trial will include eligible patients who have p53 mutated GI cancers

Tumor response to a mastermind inhibitor protein

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Background: Notch signalling is implicated in tumorigenesis prompting scientists to research and develop anti-Notch therapeutics. Drugging the Notch pathway has been a challenge due to severe G-I toxicity seen by many small-molecule inhibitors. Mastermind is a key nuclear factor that mediates Notch activity. We generated a novel protein drug, Syntana-4, that inhibits the Notch pathway at the Mastermind transcriptional level. Syntana-4 consists of the cell penetrating domain of Antennapedia, fused to a truncated peptide from Mastermind-like (MAML) that behaves in a dominant-negative fashion inhibiting Notch. Syntana-4 translocates into the cell nucleus, suppressing Notch activity and inducing apoptosis in Notch-driven cancer cells. Methods: We have conducted pharmacokinetics (PK), pharmacodynamics (PD) and toxicology studies, in combination with innovative imaging including in vivo flow cytometry and whole-body fluorescence reflectance imaging to define the behaviour of Syntana-4, determine its mode of action and establish a safety and efficacy profile in an orthotopic model of breast cancer in SCID mice based on the implantation of MDA-MB-231 cells into mammary fat pads. Samples of blood and tissues were examined for toxicity, apoptosis and immunogenicity. Results: We found that Syntana-4 was well-tolerated by normal cells and organs and was not immunogenic. Also, it was shown that free, non-internalized drug was rapidly cleared from the circulation. Whole body imaging showed that the drug in tissues was cleared within 24 hrs. Assessment of tumor growth demonstrated a reduction in tumor growth as evidenced by an overall increase of less than 50% in the intensity of fluorescence signal in the treated group compared to a 3-fold increase in signal and thus tumour size in untreated group by day 14. Conclusions: Syntana-4, a Mastermind inhibitor, was found to be well-tolerated and non-immunogenic in healthy animals. This drug targets the oncogenic Notch mechanism and can be applied across tumours with genetic defects in Notch signalling including breast, prostate, etc. We have demonstrated the utility of an innovative molecular imaging system emulating a clinical ‘phase I/II’ study in an orthotopic cancer model in order to measure the biodistribution, PK, PD, mode of action, toxicity and efficacy of a first-in-class biological therapy prior to entering the clinic. This innovative approach could be useful for accurate selection of lead drug candidates prior to entering clinical development.

Accessibility of Antigenic Sites Recognized by AUA1, HMFG1 and HMFG2 Monoclonal Antibodies: Its Influence on Antibody Binding of Live Cells

We assessed the immunoreactivity of live and alcohol-fixed monolayers of HRA-19, a rectal adenocarcinoma cell line, to the monoclonal antibodies AUA1, HMFG1 and HMFG2. Differences in staining patterns between live and alcohol-fixed colonies were found. The well-polarized cells forming the centers of the monolayer colonies showed strong membrane staining when the cells were alcohol-fixed prior to AUA1 incubation, but showed no staining when the cells were alive during the incubation. When AUA1 incubation was done both before and after alcohol fixation, membrane staining was again seen, ruling out the possibility of antigenic modulation. Incubation of live cells with AUA1 together with EDTA showed strong staining of dissociating cells. It is concluded that AUA1 antigenic sites, which on polarized cells are basolateral in location, are inaccessible to the antibody-containing culture fluid, which bathes the apical aspects of the cells, but they become accessible after alcohol fixation, or treatment with EDTA.

HMFG1 antigenic sites are located on the apical cell membrane, and accordingly, no differences were seen between incubation of live and alcohol-fixed cells when incubated with HMFG1. The antigenic sites of HMFG2 are partly intracellular, and in our monolayer model, the staining of live cells was weaker and more scarce than on alcohol-fixed cells. It is concluded that immunostaining of cytological and histological material of tumours may not adequately predict antibody binding on live cells, and thus, these findings are of importance in the context of selection of monoclonal antibodies for clinical radio-immunotargeting.

Serum Levels of C-Myc and C-Ras Oncogene Products in Normal Subjects and in Patients with Neoplastic and Non Neoplastic Conditions

A new, simple and sensitive low pH ELISA system has been developed and used to measure serum levels of c-myc and c-ras oncogene products in healthy blood donors and patients with neoplastic and non neoplastic conditions. Blood donors had significantly lower serum levels of oncogene products than patients with cancer or other pathologies (p-value < 0.01). There was, however, no difference between patients with neoplastic and non-neoplastic conditions.

Although c-myc and c-ras oncogene products in the serum appear to discriminate between healthy state and pathological conditions they do not discriminate between neoplastic and non-neoplastic conditions.

Targeting of human cancers by miRNAs delivered by mesenchymal stem cell derived microparticles

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Background: Recent data has shown that several oncogenic and tumor suppressor kinases that are deregulated in human cancers can be targeted via specific miRNA sequences. miRNAs can inhibit oncogenic kinase activity as well as upregulate tumor suppressor kinases in cancer cells, leading to inhibition of tumor processes such as invasion, migration and resistance to apoptosis. Examples include the inhibition of PLK1 activity that is overexpressed in breast, ovarian, pancreatic and colorectal cancers by the ectopic expression of miR-10b, miR-100 or miR-593, and the targeting of the increased FAK expression in breast cancer cells by miR-7. Methods: In this study, we have employed preclinical models of cancer disease and have utilized advanced genomics technologies in combination with innovative in vivo imaging techniques to conduct pharmacokinetics and pharmacodynamics studies as well as safety and efficacy studies in order to establish a mechanism of action and demonstrate that miRNA-loaded microparticles can interfere with tumor promoting kinase activity in vivo Results: Our results demonstrate that delivering specific miRNAs targeted against aberrant protein kinase activity may potentially be a novel approach to selectively inhibit cancer cell processes. Conclusions: We report the development of a new microRNA-based approach to target cancer cells by potentially interfering in multiple signaling pathways that are mediated by kinase-dependent mechanisms. We propose that therapeutic miRNA sequences can be delivered to cancer cells via microparticles (MPs) derived from umbilical cord mesenchymal stem cells (MSCs). The engineered MPs home selectively to tumor sites via specific chemokine receptors, fuse with the cell membrane and incorporate miRNA directly into the target cancer cells.

Abstract 2987: Generation of a selectively cytotoxic fusion protein against p53 mutated cancers

The most common genetic alteration in human cancer involves the p53 tumor suppressor gene resulting in defective control of cell cycle arrest and death.

The p53 protein induces a cyclin-dependent kinase (cdk) inhibitor, p21 which occupies a central position in cell cycle regulation. Cdk inhibition by p21 results in a lack of progression from the G1 to the S-phase due to the prevention of retinoblastoma (Rb) phosphorylation and subsequent inhibition of transcription factors that regulate the genes involved in DNA replication and cell-cycle progression.

It is hypothesized that the re-introduction of p21 into tumor cells will regenerate the pathway to apoptosis (programmed cell death) and inhibit proliferation since it has been suggested that overexpression of p21 results in suppression of tumor growth in vitro and in vivo.Unfortunately, p21 protein alone is unable to be administered directly in vivo and progress to the cell nuclei of cancer cells since there is no active mechanism to transport the protein. However, a number of proteins are known which can translocate across the cytoplasmic membrane of mammalian cells and into the nuclei, carrying additional cargoes with them. One of these translocating proteins is a 60 amino acid peptide corresponding to the homeodomain of the Drosophilia protein Antennapedia [ANTP].

A fusion protein (TR1) has been developed where the full-length p21 protein is attached to the antennapedia protein with a view to delivering the p21 protein into cancer cells to restore cell cycle control.

TR1 penetrated and killed cancer cells that do not express wild type p53 or p21. This included cells that were matched to cogenic parental cell lines. Antp-p21 killed cancer cells selectively that were malignant as a result of mutations or nuclear exclusion of the p53 and p21 genes and over-expression of MDM2.Non-specific toxicity was excluded by showing that TR1 penetrated but did not kill p53- or p21- wild-type cells. TR1 was not immunogenic in normal New Zealand White rabbits. Recombinant Antp peptide alone was not cytotoxic, showing that killing was due to the transduction of the p21 component of TR1. TR1was shown to penetrate cancer cells engrafted in vivo and resulted in tumour eradication when administered with chemotherapy.

TR1 may represent a new and promising targeted therapy for patients with p53-associated cancers supporting the concept that rational design of therapies directed against specific cancer mutations will play a part in the future of cancer therapeutics.

Citation Format: Agamemnon A. Epenetos, Christina Kousparou, Aleksandra Filipovic. Generation of a selectively cytotoxic fusion protein against p53 mutated cancers. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2987.

The Secret Role of microRNAs in Cancer Stem Cell Development and Potential Therapy: A Notch-Pathway Approach

MicroRNAs (miRNAs) have been implicated in the development of some if not all cancer types and have been identified as attractive targets for prognosis, diagnosis, and therapy of the disease. miRNAs are a class of small non-coding RNAs (20–22 nt in length) that bind imperfectly to the 3′-untranslated region of target mRNA regulating gene expression. Aberrantly expressed miRNAs in cancer, sometimes known as oncomiRNAs, have been shown to play a major role in oncogenesis, metastasis, and drug resistance. Amplification of oncomiRNAs during cancer development correlates with the silencing of tumor suppressor genes; on the other hand, down-regulation of miRNAs has also been observed in cancer and cancer stem cells (CSCs). In both cases, miRNA regulation is inversely correlated with cancer progression. Growing evidence indicates that miRNAs are also involved in the metastatic process by either suppressing or promoting metastasis-related genes leading to the reduction or activation of cancer cell migration and invasion processes. In particular, circulating miRNAs (vesicle-encapsulated or non-encapsulated) have significant effects on tumorigenesis: membrane-particles, apoptotic bodies, and exosomes have been described as providers of a cell-to-cell communication system transporting oncogenic miRNAs from tumors to neighboring cells and distant metastatic sites. It is hypothesized that miRNAs control cancer development in a traditional manner, by regulating signaling pathways and factors. In addition, recent developments indicate a non-conventional mechanism of cancer regulation by stem cell reprograming via a regulatory network consisting of miRNAs and Wnt/β-catenin, Notch, and Hedgehog signaling pathways, all of which are involved in controlling stem cell functions of CSCs. In this review, we focus on the role of miRNAs in the Notch-pathway and how they regulate CSC self-renewal, differentiation and tumorigenesis by direct/indirect targeting of the Notch-pathway.

Treatment of cancer and cancer stem cells by blocking the Notch pathway

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Background: Current treatments often fail to cure cancer. It has been shown (JCO, 26, June 10, 2008) that Cancer Stem Cells, (CSCs), are responsible for the initiation, metastasis and recurrence of many cancers and may be a key reason for the failure of current therapies.The NOTCH pathway is an important pathway in the development of many tumors ,and cancer stem cells in particular. Methods: We have generated genetically and synthetically a hybrid protein (Antp-DNMAML) .consisting of the truncated version of MastermindElike (MAML) that behaves in a dominant negative (DN) fashion inhibiting Notch activation, and the cell penetrating peptide Antennapedia (Antp). Results: It is demonstrated that Antp-DNMAML translocates into the nucleus and suppresses Notch activation. Attenuation of Notch signaling with AntpEDNMAML reverts the transformed phenotype, inhibits the anchorageEdependent growth, induces self contact inhibition and apoptosis in highly tumorigenic epithelial human breast cancer cells. More significantly, we provide direct evidence that inhibiting Notch signaling at the transcriptional level with the Antp-MAML protein ,suppresses the expression of downstream Notch targets, induces tumor cell apoptosis, and inhibits or eliminates human tumor growth in nude mice, without organ or systemic toxicity. Conclusions: Intracellular delivery of dominant-negative transcription complex proteins using the Antp platform is a new and specific approach for cancer therapy.

Abstract 234: Inhibition of the NOTCH transcription factor complex by a novel hybrid protein leads to effective tumor therapy

The Notch pathway has been implicated in the generation and propagation of cancer stem cells and is thus an attractive target for therapy. We have generated a hybrid protein (Antp-DNMAML) consisting of the truncated version of Mastermind-like (MAML) that behaves in a dominant negative (DN) fashion inhibiting Notch, and the cell penetrating peptide Antennapedia (Antp). Results indicate that the Antp-DNMAML translocates into the nucleus, suppresses Notch activation, reverts the transformed phenotype, inhibits the anchorage-dependent growth and induces self contact inhibition and apoptosis in tumorigenic human breast cancer cells. More significantly, there is direct evidence that inhibiting Notch signaling at the transcriptional level with the Antp-DNMAML protein, suppresses the expression of downstream Notch targets and inhibits tumor growth in nude mice, without organ or systemic toxicity. In summary, intracellular delivery of dominant-negative transcription complex proteins using the Antp platform is a new and specific approach for cancer therapy .

Citation Format: Agamemnon A. Epenetos, Christina Kousparou, Spyros Stylianou, Mahendra Deonarain, Aleksandra Filipovic. Inhibition of the NOTCH transcription factor complex by a novel hybrid protein leads to effective tumor therapy. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 234. doi:10.1158/1538-7445.AM2013-234

Generation of a selectively cytotoxic fusion protein against p53 mutated cancers

BACKGROUND

A significant number of cancers are caused by defects in p21 causing functional defects in p21 or p53 tumour-suppressor proteins. This has led to many therapeutic approaches including restoration by gene therapy with wild-type p53 or p21 using viral or liposomal vectors, which have toxicity or side-effect limitations. We set out to develop a safer, novel fusion protein which has the ability to reconstitute cancer cell lines with active p21 by protein transduction.

METHODS

The fusion protein was produced from the cell-translocating peptide Antennapedia (Antp) and wild-type, full-length p21 (Antp-p21). This was expressed and refolded from E. coli and tested on a variety of cell lines and tumours (in a BALB/c nude xenograft model) with differing p21 or p53 status.

RESULTS

Antp-p21 penetrated and killed cancer cells that do not express wild type p53 or p21. This included cells that were matched to cogenic parental cell lines. Antp-p21 killed cancer cells selectively that were malignant as a result of mutations or nuclear exclusion of the p53 and p21 genes and over-expression of MDM2. Non-specific toxicity was excluded by showing that Antp-p21 penetrated but did not kill p53- or p21- wild-type cells. Antp-p21 was not immunogenic in normal New Zealand White rabbits. Recombinant Antp peptide alone was not cytotoxic, showing that killing was due to the transduction of the p21 component of Antp-p21. Antp-p21 was shown to penetrate cancer cells engrafted in vivo and resulted in tumour eradication when administered with conventionally-used chemotherapeutic agents, which alone were unable to produce such an effect.

CONCLUSIONS

Antp-p21 may represent a new and promising targeted therapy for patients with p53-associated cancers supporting the concept that rational design of therapies directed against specific cancer mutations will play a part in the future of medical oncology.

Transcriptional inhibition of Notch signaling using cell penetrating fusion proteins

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Background: Notch signalling is deregulated in a number of cancers and is possibly involved in cancer stem cell development. It is postulated that cancers such as breast can become addicted to Notch signalling presenting opportunities for tumour-specific intervention. Due to the presence of at least 4 cell surface receptors that mediate Notch signalling, conventional targeting agents such as monoclonal antibodies cannot inhibit them all. As all the signalling cascades converge on the Notch transcriptional complex (NTC) in the nucleus, inhibition of gene expression by disrupting this machinery is an attractive strategy to overcome this redundancy. Methods: Towards this, we have developed a fusion protein based on the potent cell penetrating protein (CPP) antennapedia (Antp) recombinantly fused to a dominant-negative truncated mastermind-like protein (DN-MAML) called TR4. We have also developed a method of incorporating CPP to deliver intracellular antibody fragments against nuclear targets such as Notch and mastermind. Results: The Antp-DN-MAML protein (TR4) has similar potency to many of the gamma-secretase inhibitors being developed against this pathway but more specific for the NTC.TR4 can inhibit tumour cells in vitro and in vivo and provide some insight into the mechanism of action. Also such intracellular targets are accessible to antibodies, provided they are delivered using CPP such as antennapedia. Conclusions: .As a model system, scFvs have been raised to key epitopes in the NTC which can lead to complex inhibition and the same downstream effects as TR4.In addition, we further demonstrate that there is a more general approach to trascription factor inhibition using single-chain Fvs fused to Antp

Abstract 4364: TR4 for the treatment of human neoplasms: Novel antiNotch agent

It has been widely demonstrated that the Notch receptor signaling pathway is required for regulation and differentiation of stem cells in many tissues cell types. It is also well established that aberrant Notch signaling can lead to several human forms of cancer, including leukaemia, breast, colon, skin, cervical, and lung cancer, making Notch an attractive target for new cancer therapies. It has become clear that one of the major therapeutic targets in the Notch pathway is the cleavage of four Notch receptors, in which gamma-secretase inhibitors play a role. Unfortunately inhibition of γ-secretase complex is accompanied by many serious side effects.

In order to avoid the side effects associated with γ-secretase inhibitors and achieve an improved therapeutic effect, a more selective Notch inhibition is desirable. We have genetically engineered a fusion protein, consisting of the Drosophila transcription factor Antennapedia (ANTP) and the truncated version of Mastermind-like (MAML) that behaves in a dominant negative (DN) fashion and inhibits the Notch transactivation complex. This fusion protein, (ANTP/DN-MAML) or TR4, has been tested for its ability to target tumor cells in vitro and in vivo.

Our results indicate that targeting Notch signaling with the ANTP/DN-MAML (TR4) suppresses Notch activation, translocates into nucleus and inhibits tumor growth in mice, without significant organ or systemic toxicity.

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 4364. doi:10.1158/1538-7445.AM2011-4364

Site-specific polysialylation of an antitumor single-chain Fv fragment

Protein pharmacokinetic modulation is becoming an important tool in the development of biotherapeutics. Proteins can be chemically or recombinantly modified to alter their half-lives and bioavailability to suit particular applications as well as improve side effect profiles. The most successful and clinically used approach to date is chemical conjugation with poly(ethylene glycol) polymers (PEGylation). Here, therapeutic protein half-life can be increased significantly while retaining biological function, reducing immunogenicity and cross-reaction. Naturally occurring alternatives to such synthetic polymers could have major advantages such as lower side effects due to biodegradability and metabolism. Polysialic acid (PSA) has been investigated as a pharmacokinetic modulatory biopolymer with many successful examples in preclinical and clinical development. Single-chain Fvs (scFvs) are a choice antibody format for human therapeutic antibody discovery. Because of their small size, they are rapidly eliminated from the circulation and often are rebuilt into larger proteins for drug development and a longer half-life. Here we show that chemical polysialylation can increase the half-life of an antiplacental alkaline (PLAP) and anticarcinoembryonic antigen (CEA) scFv (F1 and MFE-23, respectively) 3.4-4.9-fold, resulting in a 10.6-15.2-fold increase in blood exposure. Amine-directed coupling of the MFE-23 scFv reduced its immunoreactivity 20-fold which was resolved by site-specific polysialylation through an engineered C-terminal thiol residue. The site-specifically polysialylated MFE-23 scFv demonstrated up to 30-fold improved tumor uptake while displaying favorable tumor:normal tissue specificity. This suggests that engineering antibody fragments for site-specific polysialylation could be a useful approach to increase the half-life for a variety of therapeutic applications.

Abstract 3332: Engineering functions in cell transduction domains: novel anticancer agents

Trojantec research has focused on the design of recombinant proteins that overcome both extracellular and intracellular limitations of other delivery systems by rapidly releasing proteins into the cytoplasm and mediating efficient nuclear translocation.

We have genetically engineered two fusion proteins; The first consisting of the Drosophila transcription factor Antennapedia (ANTP) and the truncated version of Mastermind-like (MAML) that behaves in a dominant negative (DN) fashion and inhibits Notch activation (ANTP/DN MAML) (TR4), and the second which is comprised of ANTP fused to the tumour suppressor protein p21, which is important in many key cell division processes including G1-arrest leading to apoptosis of damaged cells.

Our results indicate that drug delivery using with the ANTP cell transduction domain induces apoptosis, abolishes colony formation in soft agar, and inhibits tumor growth in mice, without organ or systemic toxicity. These studies establish TR1 and TR4 as new cancer therapeutic agents in clinical applications.

Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3332.

Antibodies targeting cancer stem cells: a new paradigm in immunotherapy?

Antibody targeting of cancer is showing clinical and commercial success after much intense research and development over the last 30 years. They still have the potential to delivery long-term cures but a shift in thinking towards a cancer stem cell (CSC) model for tumor development is certain to impact on how antibodies are selected and developed, the targets they bind to and the drugs used in combination with them. CSCs have been identified from many human tumors and share many of the characteristics of normal stem cells. The ability to renew, metabolically or physically protect themselves from xenobiotics and DNA damage and the range of locomotory-related receptors expressed could explain the observations of drug resistance and radiation insensitivity leading to metastasis and patient relapse.Targeting CSCs could be a strategy to improve the outcome of cancer therapy but this is not as simple as it seems. Targets such as CD133 and EpCAM/ESA could mark out CSCs from normal cells enabling specific intervention but indirect strategies such as interfering with the establishment of a supportive niche through anti-angiogenic or anti-stroma therapy could be more effective.This review will outline the recent discoveries for CSCs across the major tumor types highlighting the possible molecules for intervention. Examples of antibody-directed CSC therapies and the outlook for the future development of this emerging area will be given.

Modulation of antibody pharmacokinetics by chemical polysialylation

Chemical coupling of a variety of polymers to therapeutic proteins has been studied as a way of improving their pharmacokinetics and pharmacodynamics in vivo. Conjugates have been shown to possess greater stability, lower immunogenicity, and a longer blood circulation time due to the chemicophysical properties of these hydrophilic long chain molecules. Naturally occurring colominic acid (polysialic acid, PSA) has been investigated as an alternative to synthetic polymers such as poly(ethylene glycol) (PEG) due to its lower toxicity and natural metabolism. Antibodies and their fragments are a good example of the types of proteins which benefit from pharmacokinetic engineering. Here, we chemically attached differing amounts and differing lengths of short (11 kDa) and longer (22 kDa) chain colominic acid molecules to the antitumor monoclonal antibody H17E2 Fab fragment. Different coupling ratios and lengths were seen to alter the electrophoretic mobility of the Fab fragment but have a minor effect on the antibody immunoreactivity toward the placental alkaline phosphatase (PLAP) antigen. Polysialylation generally increased Fab fragment blood half-life resulting in higher tumor uptake in a KB human tumor xenograft mouse model. One H17E2 Fab-PSA conjugate had over a 5-fold increase in blood exposure and over a 3-fold higher tumor uptake with only a marginal decrease in tumor/blood selectivity ratio compared to the unconjugated Fab. This conjugate also had a blood bioavailability approaching that of a whole immunoglobulin.

Decreased intraperitoneal disease recurrence in epithelial ovarian cancer patients receiving intraperitoneal consolidation treatment with yttrium-90-labeled murine HMFG1 without improvement in overall survival

This study analyzes the site of disease recurrence in ovarian cancer patients to assess the influence of a single intraperitoneal (IP) administration of yttrium-90-labeled murine monoclonal antibody HMFG1 ((90)Y-muHMFG1) on the pattern of disease recurrence. In a large phase III trial ovarian cancer patients in complete clinical remission with FIGO stage Ic-IV were randomized between standard treatment plus a single IP (90)Y-labeled muHMFG1 versus standard treatment alone after negative second-look laparoscopy. Case report forms of all patients with disease recurrence were reviewed to determine site and date of recurrent disease. In total 447 patients were included in the study with a median follow-up of 3.5 years. Relapse was seen in 104/224 in the active and 98/223 in the control arm. Significantly fewer IP (p < 0.05) and more extraperitoneal (p < 0.05) relapses occurred in the active treatment arm. Time to IP recurrence was significantly longer (p = 0.0019) and time to extraperitoneal recurrence was significantly shorter for the active treatment arm (p < 0.001). The impact of IP radioimmunotherapy on IP relapse-free survival could only be seen in the subgroup of patients with residual disease after primary surgery (HR, 0.31; 95% CI, 0.18 to 0.53; p = 0.002). Although, there is no survival benefit for IP radioimmunotherapy as consolidation treatment for epithelial ovarian cancer, we found an improved control of IP disease, that was offset by increased extraperitoneal recurrences.

Phase III Trial of Intraperitoneal Therapy With Yttrium-90–Labeled HMFG1 Murine Monoclonal Antibody in Patients With Epithelial Ovarian Cancer After a Surgically Defined Complete Remission

Purpose

This was a multinational, open-label, randomized phase III trial comparing yttrium-90–labeled murine HMFG1 (90Y-muHMFG1) plus standard treatment versus standard treatment alone in patients with epithelial ovarian cancer (EOC) who had attained a complete clinical remission after cytoreductive surgery and platinum-based chemotherapy.

Patients and Methods

In total, 844 International Federation of Gynecology and Obstetrics stage Ic to IV patients were initially screened, of whom 447 patients with a negative second-look laparoscopy (SLL) were randomly assigned to receive either a single dose of 90Y-muHMFG1 plus standard treatment (224 patients) or standard treatment alone (223 patients). Patients in the active treatment arm received a single intraperitoneal dose of 25 mg of 90Y-muHMFG1 (target dose 666 MBq/m2). The primary end point was length of survival; secondary end points included time to relapse and safety. The study had an 80% power to detect a 15% change in survival.

Results

After a median follow-up of 3.5 years (range, 1 to 6 years), 70 patients had died in the active treatment arm compared with 61 patients in the control arm. Cox proportional hazards analysis of survival demonstrated no difference between treatment arms. In the study drug arm, 104 patients experienced relapse compared with 98 patients in the standard treatment arm. No difference in time to relapse was observed between the two study arms. Active therapy was associated with occasional grade 3 or 4 thrombocytopenia and neutropenia and grade 1 or 2 GI symptoms, abdominal discomfort, arthralgia, and myalgia.

Conclusion

A single IP administration of 90Y-muHMFG1 to patients with EOC who had a negative SLL after primary therapy did not extend survival or time to relapse.

Characterisation and internalisation of recombinant humanised HMFG-1 antibodies against MUC1

The humanised HMFG-1 immunoglobulin has been extensively developed as a clinical immunotherapeutic agent for MUC1 expressing tumours. We have constructed a single-chain Fv (scFv) and Fab fragment from this antibody and shown that both these species retain their specificity for MUC1. The scFv was less stable and less soluble than the Fab. Detailed analyses of the binding kinetics of the whole IgG and Fab fragment show that the affinity for MUC1 synthetic peptides is low (approximately 100 nM for the IgG and 10 μM for the Fab), with particularly low but similar dissociation rate constants (0.031–0.095 s⁻¹). Binding to native antigen on the cell surface is over two orders of magnitude better. Confocal immunofluorescence microscopy shows that both the IgG and Fab are internalised rapidly (the IgG is internalised within 15 min) and colocalise to early endosomes. This work provides an appreciation of the binding, internalising and trafficking kinetics, important for the development of future therapeutics based on this antibody.

Immune responses in advanced colorectal cancer following repeated intradermal vaccination with the anti-CEA murine monoclonal antibody, PR1A3: results of a phase I study

BACKGROUND AND AIMS

The aim was to determine the toxicity, clinical and immune responses to the murine monoclonal anti-carcinoembryonic antigen (CEA) antibody, PR1A3, in patients with advanced colorectal cancer.

MATERIALS AND METHODS

Fifteen patients with advanced colorectal cancer received either 0.5-, 1.0- or 5.0-mg doses of PR1A3 mixed with 10% w/v Alum adjuvant (Superfos Biosector, Denmark) intradermally at 4-week intervals for 3 months. Patient serum was assessed for anti-idiotypic (Ab2), anti-anti-idiotypic (Ab3) and human anti-mouse antibody (HAMA) reactivity. Peripheral blood mononuclear cell (PBMC) proliferation with phytohaemagglutinin (PHA), CEA and PR1A3, stimulated IL-2, IL-4 and IFN-gamma levels and PR1A3-stimulated IL-2 receptor expression during immunotherapy were determined. Comparisons were made with 16 age-matched controls without malignant disease.

RESULTS

Hyperimmune sera from 12 of the 15 patients showed Ab2 reactivity with no detectable Ab3 responses. Strong HAMA reactivity was recorded in 7 of the 15 cases with no adverse clinical effect. Delayed-type hypersensitivity (DTH) responses developed in 12 of the 15 patients. Pre-treatment PBMC proliferation with PHA was subnormal in each patient compared with controls, becoming normal (or supranormal) in all patients during immunisation (P<0.001). PBMC proliferation with CEA and PR1A3 increased during immunotherapy (P<0.001) along with stimulated production of IL-2, IFN-gamma and IL-2 receptor expression. Progressive disease was observed in 14 of the 15 patients with minimal toxicity.

CONCLUSION

PR1A3 generated limited idiotypic responses but robust DTH reactivity in most patients. In vitro PBMC proliferation with mitogens and recall antigens is greatly increased during the course of immunisation, with a shift in stimulated cytokine profile.

Antibody-guided enzyme therapy of cancer producing cyanide results in necrosis of targeted cells

A number of enzyme/prodrug activation approaches for the treatment of cancer have been reported to date with varying success. We describe progress in the development of a system based on a beta-glucosidase enzyme in combination with a naturally occurring "prodrug," the sugar linamarin, which releases the cytotoxin cyanide. A recombinant fusion protein, composed of an scFv (MFE-23) reactive against carcinoembryonic antigen (CEA) and a plant-derived beta-glucosidase (linamarase), was produced and its cytotoxic potential was investigated. The fusion protein was expressed in a supersecretory mutant strain of Saccharomyces cerevisiae and purified by affinity chromatography. Extensive functional in vitro characterisation of the fusion protein showed that it retained antigen binding activity but that its catalytic activity was impaired, a problem not related to its fusion with the scFv. Nevertheless, we demonstrated complete tumour cell killing at doses of prodrug that are completely nontoxic to nontargeted cells. Preliminary in vivo characterisation showed that extensive glycosylation of the fusion protein caused its rapid clearance through the hepatic route. Aggregational properties also led to poor pharmacokinetics. Furthermore, we present some data analysing the mode of cell death resulting from exposure to this system. Enzymic catalysis of the substrate generates cyanide, a metabolic poison that asphyxiates cells and leads them to a necrotic-like cell death. This system has been called antibody-guided enzyme nitrile therapy (AGENT).

Radioimmunoscintigraphy in patients with ovarian cancer

The use of radiolabeled monoclonal antibodies (MoAbs) has significantly improved the ability to detect tumor antigens, thus improving in vivo tumor diagnosis and treatment. The management of ovarian carcinoma still poses a challenging medical problem. Clinical trials using radioimmunoscintigraphy or a hand-held gamma detection probe intraoperatively were performed in patients with clinical evidence of primary or recurrent ovarian cancer. Immunoscintigraphy of ovarian cancer lesions has been performed mainly with 99mTc, 111In and 123I labeled with HMFG1, HMFG2, OC-125, B72.3, H17E2, OVTL3, MoAb170, Mov18 and other MoAbs. Antibody guided imaging using radioimmunoscintigraphy has demonstrated improved targeting of ovarian cancer, resulting in a highly sensitive and specific method. However, it is not yet known which type of MoAb is the most efficient for radioimmunoscintigraphy. Since these tumors represent a potentially curable disease, radioimmunoscintigraphy could contribute mainly to accurate staging as a supplementary to conventional diagnostic methods, as well as for the localization of active disease after chemotherapy and monitoring for the presence of recurrent disease. Nevertheless, prospective studies in a large number of patients should be undertaken in order to further evaluate the diagnostic contribution of this approach.

A recombinant cytotoxic chimera based on mammalian deoxyribonuclease-I

A number of mammalian proteins with suitable biological activities have been considered for use in targeted tumour therapy. Deoxyribonuclease-I (DNase-I), an endonuclease that degrades double-stranded DNA, represents an attractive candidate for tumour targeting since it is normally non-toxic yet could be highly cytotoxic when redirected to the cell nucleus. Our aim was to investigate the cytotoxic potential of mammalian DNase-I and its possible use in tumour-targeting strategies for cancer therapy. A chimeric molecule comprising a scFv reactive against the human placental alkaline phosphatase (hPLAP) and bovine pancreatic DNase-I was designed and investigated. The development of a tightly controlled system for the bacterial expression of DNase-I and its chimera is described. The production and purification of active DNase-I from the soluble cell fraction and significant yields from the insoluble fraction by isolation and refolding are described. The construction, expression, purification and in vitro characterisation of an anti-PLAP scFv-DNase-I chimera is also described. This molecule was shown to possess both antigen-binding and DNA-degrading activity in in vitro assays, thus combining the specific cell-targeting properties of the scFv and the potent, highly catalytic activity of the endonuclease. Furthermore, this chimeric molecule was highly cytotoxic in vitro in cells expressing the PLAP antigen. Targeting mammalian DNase-I provides a novel therapeutic strategy for selective cell killing, with the promise of less systemic toxicity and immunogenicity than currently used immunotoxins.

Development of a novel bi-specific monoclonal antibody approach for tumour targeting

To overcome the disadvantages of bi-specific antibody methodologies in vivo, a novel antibody approach has been designed to improve tumour targeting and effector to target ratio. The technique involves biotinylated anti-CD3 Fab fragments and streptavidinylated anti-tumour monoclonal antibodies (mAbs) that can spontaneously form cross-links. We describe here a method for the direct cross-linking of sulphydryl-conjugated HMFG1 (anti-MUC1 mucin mAb) to streptavidin by sulphosuccinimidyl-4-(N-maleimidomethyl) cyclohexane-1-carboxylate. Fab fragments generated by papain digestion of the 1452C11 antibody (anti-CD3 mAb without Fc to avoid peripheral activation of T-cells) were biotinylated with NHS-Iminobiotin. MUC1-transfected BALB/c breast cancer cell lines 413BCR and 425CCR and the parental cell line (410.4) were labelled with streptavidinylated mouse anti-MUC1 mucin mAb. BALB/c effector T-cells were separately labelled with biotinylated anti-CD3 Fab fragments (1452C11) and mixed with tumour cells in different effector to target ratios. Percentage of killing was assessed using the 51Cr cytotoxicity assay. Seventy per cent lysis was measured in the case of 413BCR (high MUC1 mucin expressor) and 40% in the case of 425CCR (low expressor) cell line. No lysis was apparent in the MUC1 negative cell line. These results demonstrate that the novel T-cell redirecting approach we have developed can produce effective immune lysis of target cells in vitro.

Radioimmunoscintigraphy in patients with ovarian cancer

The targeting potential of three different monoclonal antibodies (MAbs) was assessed in patients with ovarian cancer. HMFG1, OC-125 and H17E2 labelled with 111In or 123I were evaluated prospectively for their ability to localize ovarian tumour. Forty two patients with ovarian cancer, aged 40-78 years (median = 58 years) were studied using OC-125 (n = 9), HMFG1 (n = 11) and H17E2 (n = 22). Imaging data were compared with the CT and the surgical findings. Presence of tumour was confirmed in 35/42 (83%) patients (8/9 OC-125, 10/11 HMFG1 and 17/22 H17E2) and correlated well with the conventional radiology diagnostic methods. One patient with a negative H17E2 scan and a large abdominal mass detected at laparotomy revealed a PLAP-negative tumour on immunohistochemistry. Scintigraphy revealed the presence of active disease, confirmed by laparotomy/laparoscopy in 6/8 patients considered to be in clinical remission. The sensitivity of the method was high enough and the diagnostic contribution of this approach should be further evaluated.

Intravesical administration of radiolabelled tumour-associated monoclonal antibody in bladder cancer

Considerable progress has been made over the past decade in the use of tumour-associated monoclonal antibodies (mAbs) as carriers of cytotoxic agents in the management of several malignancies. In the present study we investigated the tumour localization and biodistribution of the mAb HMFG1 to bladder cancer following intravesical administration. HMFG1, which has been raised against the polymorphic epithelial mucin (PEM), was labelled with 125I and administered intravesically 2 h and 24 h before cystoscopy. During cystoscopy, biopsies were taken from the normal bladder and the malignant lesion. Tissue samples were tested for HMFG1 immunostaining and for radioactivity with the use of a gamma-counter. The mean ratio of tumour to normal uptake for 125I-HMFG1 was 5.81 +/- 1.23, at 2 h and 2.17 +/- 0.42 at 24 h. No radioactivity was detected in the blood. We conclude that HMFG1 could be used intravesically for the successful delivery of a cytotoxic agent.

Use of monoclonal antibodies for the diagnosis and treatment of bladder cancer

Although the management of cancer by exploiting properties distinguishing neoplastic and normal cells has always been an attractive concept, it was the development of hybridoma technology and the resulting tumor-associated monoclonal antibodies (MAbs) that offered new prospects for this strategy. Twenty years later, some of the applications of MAbs in oncology are now part of the everyday diagnosis and treatment, while others are the subject of intensive investigation. We reviewed the current applications of MAbs in the diagnosis and treatment of bladder cancer and attempted to put the issue into perspective, with particular presentation of their therapeutic potential.

Antibody directed enzyme prodrug therapy (ADEPT): a review of the experimental and clinical considerations

Over the last decade several attempts have been made to generate an active drug from an inactive precursor, by the action of an enzyme present predominantly at the tumour site. The aim was to develop a new, less cytotoxic strategy for the treatment of cancer, by exploiting properties distinguishing neoplastic and normal cells. In fact, monoclonal antibodies were used to carry enzymes at the tumour sites, in a two-step approach, known as Antibody Directed Enzyme Prodrug Therapy (ADEPT). We reviewed the experimental and clinical considerations of this strategy and we presented its problems and limitations. We concluded that ADEPT holds the potential of an effective and relatively non-toxic treatment of cancer and it is expected that the research which is in progress will make ADEPT an important element of the anticancer armament.

In vitro cytotoxicity following specific activation of amygdalin by beta-glucosidase conjugated to a bladder cancer-associated monoclonal antibody

We describe a novel version of antibody-directed enzyme prodrug therapy (ADEPT), with the use of amygdalin as prodrug. Amygdalin is a naturally occurring cyanogenic glycoside, which can be cleaved by sweet almond beta-glucosidase to yield free cyanide. If amygdalin could be activated specifically at the tumour site, then malignant cells would be killed without the systemic toxicity usually associated with chemotherapy. To this end, we have conjugated beta-glucosidase to a tumour-associated monoclonal antibody (MAb) (HMFG1) and the conjugate has been tested in vitro for specificity and cytotoxicity subsequent to activation of amygdalin. Amygdalin was cytotoxic to HT1376 bladder cancer cells only at high concentrations, whereas the combination of amygdalin with HMFG1-beta-glucosidase enhanced the cytotoxic effect of amygdalin by 36-fold. When 2 concentrations of HMFG1-beta-glucosidase were compared, the toxic effect was dose dependent. The cytotoxicity of amygdalin was also enhanced by the MAb-enzyme conjugate even when the unbound conjugate was removed from the medium prior to exposure to amygdalin and the cells were washed. In addition to the cytotoxic effect, we also demonstrated specificity, using a MAb-enzyme conjugate that does not recognise the HT1376 bladder cancer cells. Finally, we studied the cytotoxic effect of the conjugate in co-culture of HMFG1-positive and-negative cell lines (HT 1376 and U87MG cells). We demonstrated that the rate of surviving cells corresponds well to the percentage of U87MG (HMFG1-negative) cells in the flask. Our findings indicate that ADEPT is more effective than non-directed enzyme activation of a prodrug and can result in a non-toxic cancer therapy.

Improving tumour targeting and decreasing normal tissue uptake by optimizing the stoichiometry of a two-step biotinylated-antibody/streptavidin-based targeting strategy: studies in a nude mouse xenograft model

We aimed to study in detail the in vivo stoichiometry of the individual elements of the 2-step streptavidin based approach to tumour targeting, in a nude mouse xenograft model, by the administration of a first step consisting of biotinylated anti-tumour specific antibody and a second step consisting of streptavidin. This process was undertaken to identify the optimum conditions for radiotherapeutic tumour targeting using this approach. Antibody was biotinylated to various degrees (1-25 biotins per antibody). Protein stoichiometry of the 2 steps was studied over a range of 2 logs. Both steps, i.e., the biotinylated-antibody (1st step) and streptavidin (2nd step) were radiolabelled (125I and 131I, respectively). A 24-hr interval between 1st and 2nd step was studied, animals being killed 24 hr after the 2nd step. Streptavidin excess led to a decrease in levels of monobiotinylated-antibody in the circulation and in the tumour. Biotinylated-antibody excess led to an increase in circulating levels of streptavidin, a decrease in renal uptake of streptavidin and increased targeting of streptavidin to tumour. At a constant protein molar ratio of biotinylated antibody to streptavidin of 10:1, increasing biotinylation density resulted in an increase in circulating levels, increase in tumour uptake, decrease in renal uptake and increase in liver uptake of streptavidin. As early as 24 hr, the tumour-to-blood ratios of streptavidin already exceeded 1 (max 1.27). Compared with antibody tumour-to-blood ratios, they were better by a factor of between 2 and 3. Tumour-to-normal tissue ratios of radiolabelled streptavidin (with the exception of liver) were also significantly improved when polybiotinylated-antibody was administered first. We have thus shown that the 2-step biotinylated antibody/streptavidin approach can lead to a significant increase in absolute amounts of activity in the tumour under appropriate stoichiometric conditions. This was accompanied by high levels of circulating streptavidin and relatively favourable tumour-to-blood and normal tissue ratios of streptavidin.

Imaging of metastatic melanoma utilising a technetium-99m labelled RGD-containing synthetic peptide

Integrins are cell-surface glycoproteins found in different forms on all cells except erythrocytes. Integrins bind to cell adhesion molecules and to proteins found in the extracellular matrix. A tripeptidic sequence Arg-Gly-Asp (RGD) is often the primary site of recognition by integrins which are expressed on tumour cells and are responsible for tumour invasion and metastasis. A synthetic decapeptide designated alpha P2 containing two RGD sequences radiolabelled with technetium-99m was used to image malignant melanoma in vivo. Fourteen patients previously diagnosed with metastatic melanoma underwent gamma camera imaging 20-180 min following intravenous administration of the radiolabelled synthetic decapeptide alpha P2. Six out of eight (6/8) of the lymph node metastases (75%) and all other neoplastic sites (11 sites) were successfully imaged, with the exception of three sites in the mediastinal area which were not positively imaged. In two cases there was false positive uptake in the rounded pigmented areolar/nipple area. In three cases (seven sites) the peptide scan confirmed the absence of disease in suspected lesions (true-negative). The synthetic peptide was rapidly removed from the circulation by filtration through the kidneys and excretion in the urine. No toxicity or adverse events were recorded. Radiolabelled alpha P2 peptide, which binds specifically to adhesion molecules on tumours, can be used for the in vivo detection of neoplastic metastases.

Monoclonal antibody targeting of ovarian carcinoma

The ability to effectively define disease status in ovarian cancer after initial therapy or to selectively screen high-risk populations remains a major challenge for in vivo monoclonal antibody (mAb)-targeted approaches. Antitumour murine mAbs (HMFG1, HMFG2, H317, and H17E2) and the reshaped human antibody Hu2PLAP (against placental alkaline phosphatase; PLAP), labelled with indium-111 and iodine-123, were evaluated for their ability to localise ovarian tumours in sequential studies of our group. Thirty patients with ovarian cancer, aged 40-78 years (median 60 years) were studied with HMFG1/G2: 11, and H317/H17E2: 19 murine mAbs. Six patients with ovarian cancer aged between 36 and 65 years (median 49 years) were studied with the reshaped human Hu2PLAP mAb (5 patients) or the murine H17E2 mAb (2 patients) labelled with 111In via a new macrocyclic chelating agent (DOTA). One of these was imaged twice, with H17E2- and Hu2PLAP-DOTA-111In, respectively. In 20 out of 22 patients with radiologically measurable ovarian cancer, the presence of tumour was confirmed by the murine mAb scan and correlated well with the findings of conventional radiology diagnostic methods. One of these patients with a negative H17E2 scan and a large abdominal mass at laparotomy was found to have a PLAP-negative tumour on immunohistochemistry. Additionally, the antibody scan revealed the presence of active disease, confirmed at laparotomy/laparoscopy, in 6 out of 8 patients considered to be in clinical complete remission. Best images were obtained at 24 and 48 h after the 123I and 111In mAbs, respectively. Successful imaging with the reshaped human antibody, Hu2PLAP, was seen in 2 patients with PLAP-positive tumours. Antibodies to DOTA developed in 2 patients. In conclusion, immunolocalisation of ovarian tumours is feasible with both murine and reshaped human mAbs. The sensitivity and specificity of the method appear very high in this pilot study, and in view of the absence of toxicity, the diagnostic contribution of this approach should be evaluated prospectively. Given the low number of patients without surgically detectable disease in the present study, future investigations should include more patients with no evidence of disease in order to provide more meaningful estimates of specificity.

Design, characterization and anti-tumour cytotoxicity of a panel of recombinant, mammalian ribonuclease-based immunotoxins

Bovine seminal ribonuclease (BSRNase) is an unusual member of the ribonuclease superfamily, because of its remarkable anti-tumour and immunosuppressive properties. We describe here the construction, expression, purification and characterization of a panel of six immunotoxins based upon this enzyme and show that we can increase its anti-tumour activity by over 2 x 10(4)-fold. This is achieved by improving tumour cell targeting using a single-chain Fv (scFv) directed against the oncofetal antigen placental alkaline phosphatase. As well as the simple scFv-BSRNase fusion protein, we have constructed five other derivatives with additional peptides designed to improve folding and intracellular trafficking and delivery. We find that the molecule most cytotoxic to antigen (PLAP)-positive cells in vitro is one that contains a C-terminal 'KDEL' endoplasmic reticulum retention signal and a peptide sequence derived from diphtheria toxin. All these molecules are produced in Escherichia coli (E. coli) as insoluble inclusion bodies and require extensive in vitro processing to recover antigen binding and ribonuclease activity. Despite incomplete ribonuclease activity and quaternary assembly, these molecules are promising reagents for specific chemotherapy of cancer and are potentially less harmful and immunogenic than current immunotoxins.

Radioimmunotherapy after chemotherapy compared to chemotherapy alone in the treatment of advanced ovarian cancer: a matched analysis

Ovarian cancer has an overall five-year survival of around 30% in spite of complete remissions being obtained after optimal surgery and platinum-based chemotherapy. Previous studies have indicated a survival advantage for patients treated with radiolabelled monoclonal antibodies (radioimmunotherapy). We report here on the survival of patients who received single-dose intraperitoneal radioimmunotherapy after having achieved complete remission with standard management. Twenty-five patients with epithelial ovarian cancer, stages Ic-IV, received adjuvant intraperitoneal radioimmunotherapy following completion of conventional chemotherapy. On achieving complete remission they receive once 25 mg of HMFG1 labelled with 18 mCi/m2. Controls for cases were sought from the database of the North Thames ovary group (NTOG). Controls were selected on the basis of stage, histological grade and type, and age of patient at diagnosis. Kaplan-Meier survival plots were constructed for cases and controls and subjected to statistical analysis with the log-rank test. Additionally, using a database of 84 NTOG patients known to be disease-free at the end of chemotherapy, estimated survival curves were constructed using Cox's proportional hazards regression model. Close matches were found for 20 of the 25 patients. Median survival has not been reached at a median follow-up of 59 months for cases and 27 months for controls. Survival at five years is 80% for cases and 55% for controls (p=0.0035). The Cox model estimates long-term (10-year) survival of 70% for patients who received radioimmunotherapy, compared to 32% for those that did not (p=0.003). All patients developed serological evidence of human anti-mouse antibody (HAMA). This study shows a likely survival benefit for patients with ovarian cancer who receive intraperitoneal radioimmuno-therapy in the adjuvant setting.

A pilot pharmacokinetic and immunoscintigraphic study with the technetium-99m-labeled monoclonal antibody BC-1 directed against oncofetal fibronectin in patients with brain tumors

BACKGROUND

Preliminary experiments in an animal model have shown the favorable tumor targeting potential in vivo of radiolabeled BC-1, an immunoglobulin (Ig)G1 monoclonal antibody (MoAb) that recognizes the human fibronectin isoform (B+) containing the ED-B oncofetal domain. This antigen has extremely restricted distribution in normal adult tissues. Instead, it is highly expressed in fetal and tumor tissues, especially in high grade astrocytomas and malignant gliomas of the brain, in which the process of neoangiogenesis linked to tumor growth is particularly important.

METHODS

This study was carried out with five patients who had malignant brain tumors (four gliomas and one malignant angioblastic meningioma). The BC-1 MoAb was labeled with technetium-99m (99mTc) by MDP transchelation. Planar and single photon emission computed tomography (SPECT) imaging was acquired at 4-6 and 20 hours after intravenous injection of about 450 MBq/0.2 mg 99mTc-BC-1 and was compared with the nonspecific indicator of blood-brain barrier disruption, 99mTc-diethylenetriamine pentaacetic acid (DTPA). Plasma pharmacokinetic analysis was based on serial blood sampling. All patients underwent potentially curative surgery at the end of the study.

RESULTS

The plasma clearance curves were biexponential, with average T(1/2) values of 2-4 hours and 28-33 hours, respectively. 99mTc-BC-1 showed very low nonspecific uptake in the bone marrow, liver, and spleen. Planar and SPECT imaging with 99mTc-BC-1 visualized brain tumors in all patients, with a pattern of intratumor distribution that specifically identified areas of peripheral tumor growth more accurately than the nonspecific indicator, 99mTc-DTPA. Tumor uptake of 99mTc-BC-1 was correlated with the expression of the specific oncofetal fibronectin, as shown by immunohistochemistry on surgical samples.

CONCLUSIONS

These results indicate the diagnostic potential of MoAb 99mTc-BC-1 for immunoscintigraphy in cancer patients, at least when neoangiogenesis induced by cancer is particularly important.

Redesigned anti-human placental alkaline phosphatase single-chain Fv: soluble expression, characterization and in vivo tumour targeting

Although much progress has been made in the production of recombinant antibodies and their fusions, there are still problems with solubility and folding. Useful antibodies produced from cloned hybridomas do not always result in scFvs behaving favourably. We report here further work on an scFv (H17E2) against the oncofetal antigen human placental alkaline phosphatase. The overall expression was greatly improved and the H17E2 scFv was redesigned by manipulation of the interdomain linker, resulting in much higher expression levels of the soluble scFv in its active conformation at 0.2-0.5 mg/l of bacterial culture. We show that the new soluble version of this scFv has similar characteristics to the refolded version in terms of antigen and tumour cell binding, stability and in vivo pharmacokinetics. The final tumour uptake behaviour of these scFvs is superior to that of the parental whole antibody with respect to tumour:organ ratios, but still requires further development before considering it as a suitable molecule for clinical use in ovarian or testicular cancer.

Enhanced in vivo immunogenicity induced by an antibody to the IL-4 receptor-associated gp200-MR6 molecule

Four murine IgG1 monoclonal antibodies, each with specificity for a human tumour-associated antigen, have been tested for their in vivo immunogenicity using a rabbit model. Surprisingly, one of these antibodies, MR6, was significantly more immunogenic than the remaining three reagents. This enhanced MR6 immunogenicity was not restricted to the immunoglobulin molecule itself, but also applied to a hapten (fluorescein isothiocyanate, FITC) when conjugated to the monoclonal antibody. In addition, the secondary immune response to an independent antigen, human haemoglobin, was higher when the antigen was administered simultaneously with MR6 than when co-injected with an isotype-matched control monoclonal antibody. The presence of the target antigen, gp200-MR6, on both rabbit and human leucocytes and epithelium, and its known association with human IL-4 function, raises the possibility that antibody MR6 may not only target immunogens to antigen-presenting cells, but may also enhance the ability of these cells to present antigen to the immune system. Antibodies to the gp200-MR6 may therefore find important clinical application as in vivo adjuvants.

E-cadherin expression in bladder cancer using formalin-fixed, paraffin-embedded tissues: correlation with histopathological grade, tumour stage and survival

To determine the potential prognostic value of epithelial cadherin (E-cadherin), a Ca(2+)-dependent cell-cell adhesion molecule, we have analysed its immunoreactivity and cellular localisation in 67 transitional cell carcinomas (TCC) using an avidin-biotin immunoperoxidase technique on formalin-fixed, paraffin-embedded tissues. These results were correlated with histopathological grade, tumour stage, presence of metastases and survival. In addition, 10 cystitis and 11 normal bladder biopsies were evaluated as controls. E-cadherin was expressed in a normal membranous pattern in all normal and 7 of 10 cystitis biopsies. Loss of normal surface E-cadherin expression was found in 3 of 15 superficial tumours and in 48 of 52 invasive cancers. Abnormal immunoreactivity was strictly related to tumour differentiation and stage. Fifteen of 20 well-differentiated (grade I) tumours showed preserved membranous E-cadherin immunoreactivity, while 46 of 47 moderate and poorly differentiated tumours (grades II and III) demonstrated abnormal staining patterns. Loss of membranous E-cadherin immunoreactivity was also associated with advanced tumour stage. There was a significantly higher 5-year survival rate for patients with preserved membranous staining compared with patients with abnormal staining.

Construction, expression and characterisation of a single chain anti-tumour antibody (scFv)-IL-2 fusion protein

We describe the production and preliminary characterisation of a fusion protein between interleukin-2 and a single-chain Fv version of the H17E2 anti-placental alkaline phosphatase (PLAP) antibody. This molecule could be used to target interleukin-2 to PLAP-expressing tumours.

Genetic delivery of enzymes for cancer therapy

For many years, antibodies have been examined as means to deliver cytotoxic proteins to kill target cells (immunotoxins). More recently, there have been studies on enzymes that convert prodrugs to active drugs to kill target cells. The advances in gene therapy strategies now allow one to deliver the gene for the protein or enzyme as an alternative. This technique, although in its infancy, promises to overcome some of the problems associated with antibody-mediated delivery. Thymidine kinase and cytosine deaminase are some of the enzymes currently being exploited in this way, but more are on the horizon. However, more research is still needed to enable full exploitation of the transcriptional differences between tumour and normal cells so that more existing cancers can be treated in this way.

DNA vaccination for cancer treatment

The recent finding that inoculation with plasmids encoding a variety of proteins leads to T cell and antibody responses in vivo against these proteins provides a novel means of active specific immunisation by plasmid vaccination. The demonstration that both major histocompatibility complex (MHC) Class I- and Class II-mediated interactions can be elicited may make this approach suitable for development of tumour vaccines. Plasmids may prove to be an efficient way to build 'subunit' and multi-subunit vaccines based on the genetic changes that occur in carcinogenesis. Expression of DNA encoding fragments of tumour-specific proteins as neo-antigens or surrogate antigens in a novel context may be a means of breaking immunological tolerance and lead to the generation of tumour-specific immune responses.

Direct technetium-99m labeling of three anticancer monoclonal antibodies: stability, pharmacokinetics and imaging

Monoclonal antibodies (MAbs) directly labeled with 99mTc have been used in a number of clinical immunoscintigraphic investigations. Three anti-cancer MAbs were radiolabeled with 99mTc using a reduction-mediated technique. The stability, biodistribution and in vivo pharmacokinetics were assessed and compared with the same antibodies labeled with 125I.

METHODS

Immunoreactivity data were obtained by ELISA and RIA. Homogeneity and stability of radiolabeled antibodies (in vitro and in vivo) were measured by size-exclusion, fast protein liquid chromatography and SDS-PAGE. Pre-clinical, in vivo investigations utilized the nude mouse/HEp2 xenograft model, and clinical imaging and pharmacokinetic data were obtained from patients with confirmed or suspected lesions.

RESULTS

Both 99mTc- and 125I-labeled antibodies were shown to be homogeneous and stable, although 99mTc-labeled antibody fragments were detected by SDS-PAGE. Pharmacokinetic studies in patients revealed a significant difference in the clearance rates between 99mTc- and 125I-labeled antibodies, with those labeled with 99mTc having a shorter biological half-life, indicating that the 99mTc-labeled antibodies may be less stable than the iodinated ones. Nevertheless, specific tumor localization was successfully demonstrated in nude mice bearing a human tumor xenograft using 125I- and 99mTc-labeled H17E2 antibody. Furthermore, in the clinic, using 99mTc-labeled HMFG1 and 1A3, successful imaging was achieved in 12 out of 19 patients with lesions for which these antibodies were specific.

CONCLUSION

Anticancer MAbs radiolabelled using this reduction-mediated technique are suitable agents for clinical, immunoscintigraphic investigations.

Anti-chelate antibodies after intraperitoneal yttrium-90-labeled monoclonal antibody immunoconjugates for ovarian cancer therapy

The development of stable chelating agents for metal isotopes (e.g., 90Y) such as CITC-DTPA, a benzyl-analog of DTPA, allowed us to evaluate the efficacy of 90Y-labeled HMFG1 MAb administered intraperitoneally in patients with ovarian cancer. Our previous studies of 90Y-HMFG1 antibody, however, showed that all patients developed anti-chelate antibody responses (to the macrocycle benzyl-DOTA), resulting in clinical side effects in a significant percentage of this group.

METHODS

We evaluated the immunogenicity of CITC-DTPA (administered to 12 patients as 90Y-HMFG1-CITC-DTPA after coupling it to HSA using solid-phase ELISA.

RESULTS

Eleven of 12 evaluable patients developed anti-CITC-DTPA antibodies. Five patients (approximately 40%) developed hypersensitivity syndrome, most likely due to a type III immune reaction (serum sickness). Most patients had a low titer of pre-existing anti-chelate response which correlated positively with post-therapy response levels (p = 0.001). IgM anti-CITC-DTPA antibodies developed 2 wk while IgG antibodies developed 3 wk after treatment. Western blot analysis of post-therapy sera revealed a reaction with HSA-CITC-DTPA (60 kDa band) and no reaction with HSA or HSA-DTPA, whereas pre-therapy sera of the same patients were negative to all antigens.

CONCLUSION

CITC-DTPA is immunogenic in patients after intraperitoneal administration of 90Y-CITC-DTPA labeled MAbs. Self-limiting clinical side effects consistent with a serum sickness-like immune reaction were observed in 5 of 12 patients.

Radioimmunotherapy of ovarian cancer

Despite the advances in the management of ovarian cancer, the disease remains the leading cause of death from gynecological malignancies. As it generally remains confined to the peritoneal cavity, ovarian cancer is an attractive target for radioimmunotherapy via the intraperitoneal route of administration. Several clinical trials have been carried out investigating radiolabeled monoclonal antibodies and the results seem promising, especially in patients with small-volume residual disease after conventional therapy. Intraperitoneal radioimmunotherapy has yet to prove itself as an important part of the treatment of ovarian cancer.