Agamemnon A. Epenetos

Antibody-guided irradiation of advanced ovarian cancer with intraperitoneally administered radiolabeled monoclonal antibodies.

Twenty-four patients with persistent epithelial ovarian cancer after chemotherapy with or without external beam irradiation, were treated with intraperitoneally administered 131I-labeled monoclonal antibodies HMFG1, HMFG2, AUA1, H17E2, directed against tumor-associated antigens. Acute side effects were mild abdominal pain, pyrexia, diarrhea, and moderate reversible pancytopenia. One patient developed a subphrenic abscess requiring surgical drainage. Eight patients with large volume disease, ie, greater than 2 cm tumor diameter, did not respond to antibody-guided irradiation and died of progressive disease within 9 months of treatment. Sixteen patients had small-volume (less than 2 cm) disease at the time of treatment with radiolabeled antibody. Seven patients failed to respond, and of nine initial responders, four patients remain alive and free from disease 6 months to 3 years from treatment. Analysis of the data on relapse indicated that doses greater than 140 mCi were more effective than lower doses. We conclude that the intraperitoneal administration of 140 mCi or more of 131I-labeled tumor-associated monoclonal antibodies represents a new and potentially effective form of therapy for patients with small-volume stage III ovarian cancer.

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.

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 tumour 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 tumours 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 tumour types highlighting the possible molecules for intervention. Examples of antibody-directed CSC therapies will be given and the outlook for the future development of this emerging area will be given.

Exploiting altered glycosylation patterns in cancer: Progress and challenges in diagnosis and therapy

In this review, we describe the changes in glycosylation and expression of mucins, in particular, polymorphic epithelial mucin (PEM), the product of the MUC1 gene in tumours and normal tissues. In addition, some of the areas where exploitation of altered glycosylation patterns in tumour mucins can be used for the better understanding of the disease process and be applied for in vivo diagnosis and therapy are addressed.

Intraperitoneal radioimmunotherapy for ovarian cancer: pharmacokinetics, toxicity, and efficacy of I-131 labeled monoclonal antibodies

Thirty-six patients with ovarian cancer were treated with intraperitoneal I-131 labeled monoclonal antibodies to tumor associated antigens. The activity of I-131 administered was increased from 20 mCi to 158 mCi and the pharmacokinetics and toxicity evaluated. Five patients who had developed HAMA (Human Antimouse Antibodies) were retreated, and the pharmacokinetics and toxicity of the first and second treatment compared. Patients receiving their first therapy (HAMA negative), had a maximum of 25% (range 19.8-39.8%) of the injected activity in their circulation. This was accompanied by severe marrow suppression at I-131 activities over 120 mCi. The 5 HAMA positive patients had only 5% injected activity in the systemic circulation (range 3.8-6%), with rapid urinary excretion and neglible marrow suppression. In 31 patients with assessable disease there were no responses in 8 patients with gross disease (nodules greater than 2 cms), partial responses in 2 out of 15 patients with nodules less than 2 cms, and complete responses in 3 out of 6 patients with microscopic disease. The non specific radiation dose to the peritoneal cavity was estimated to be less than 500 cGy by lithium fluoride TLD, and could not be expected to account for the responses seen.

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 (90Y‐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 90Y‐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.

Indium-111 labelled monoclonal antibody to placental alkaline phosphatase in the detection of neoplasms of testis, ovary, and cervix

A monoclonal antibody (H17E2) against placental alkaline phosphatase (PLAP) and testicular placental-like alkaline phosphatase was labelled with indium-111 and used in radioimmunoscintigraphy of 15 patients known or suspected to have germ-cell carcinoma of the testis or carcinoma of the ovary or cervix. Good images of neoplastic lesions were obtained in most patients with active disease. In 1 patient with testicular teratoma and elevated human chorionic gonadotropin who had a normal computed tomography scan, the labelled antibody located microscopic disease in a lymph node, which was then removed. No false positive localisation was seen in patients with PLAP-negative tumours or sites of inflammation. This method may be helpful in the diagnosis, staging, and monitoring of PLAP-positive neoplasms of testicular, ovarian, and cervical origin.

In vitro cytotoxicity following specific activation of amygdalin by β-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 β‐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 β‐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‐β‐glucosidase enhanced the cytotoxic effect of amygdalin by 36‐fold. When 2 concentrations of HMFG1‐β‐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 (HT1376 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. Int. J. Cancer 78:712–719, 1998.

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.

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.