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P Thorpe

Publications and source records attributed to P Thorpe.

At least 37 records · Page 2Linked to original sources
PubMed1991

Immunotoxins constructed with anti-CD25 monoclonal antibodies and deglycosylated ricin A-chain have potent anti-tumour effects against human Hodgkin cells in vitro and solid Hodgkin tumours in mice.

Twenty-three monoclonal antibodies (MAbs) against the IL-2 receptor alpha-chain (CD25) were evaluated as ricin A-chain immunotoxins for the treatment of Hodgkin's disease. Primary screening used an indirect assay in which the cells were treated with the test antibody followed by a Fab' immunotoxin against mouse immunoglobulin. This screening identified 5 MAbs which inhibited protein synthesis in L540 Hodgkin cells by 50% at a concentration (IC50) of 6 x 10(-11) M or less: RFT5 gamma 1, RFT5 gamma 2a, B-B10, B-F2 and B-G3. These MAbs were then linked directly to deglycosylated ricin A-chain (dgA) and were confirmed to have potent and specific toxicity for L540 cells. The immunotoxins had the following potency order: RFT5 gamma 1 greater than RFT5 gamma 2a greater than B-B10 greater than B-F2 greater than B-G3. The most effective immunotoxin, RFT5 gamma 1.dgA, had an IC50 value of 7 x 10(-12) M, which is the same as that of whole ricin. In vivo, a single intravenous injection of 48 micrograms of RFT5 gamma 1.dgA, RFT5 gamma 2a.dgA, B-B10.dgA or B-F2 induced lasting complete remissions in 78, 66, 50 and 44%, respectively, of nude mice bearing subcutaneous solid L540 tumours of 0.7 cm diameter. Two tumours which regrew after B-B10.dgA treatment were re-established in tissue culture. Both had reduced sensitivity to B-B10.dgA in vitro but not to immunotoxins recognizing different antigens on Hodgkin cells. The MAbs that produced the most potent immunotoxins, RFT5 gamma 1, RFT5 gamma 2a and B-B10, had no significant cross-reactivity with normal human tissues outside the lymphoid system as judged from indirect immunoperoxidase staining of frozen sections. By contrast, B-F2 strongly stained normal human renal tubules.

Animals↗
PubMed1991

The GLP large scale preparation of immunotoxins containing deglycosylated ricin A chain and a hindered disulfide bond.

The large scale preparation of two second generation immunotoxins containing murine monoclonal antibodies and deglycosylated ricin A chain is described. The procedure for the preparation of immunotoxins consists of the derivatization of antibody with SMPT and reduction of dgA with DTT followed by their reaction to establish a hindered interchain disulfide bond. The purification of the immunotoxin includes affinity chromatography on Blue-Sepharose to remove the free antibody and gel filtration on Sephacryl S-200HR to remove any high molecular weight material and free dgA. The two immunotoxins were prepared by GLP procedures and tested for yield, composition, purity, sterility and biological activity.

Antibodies, Monoclonal↗
PubMed1991

Resistance of myeloid leukaemia cell lines to ricin A-chain immunotoxins.

Nineteen monoclonal antibodies that recognize antigens on myeloid leukaemia cells were screened upon HL60, KG1, U937 and K562 cells for their ability to form effective ricin A-chain immunotoxins. The screening was performed using an indirect assay in which the cells were treated firstly with the test antibody and then with a Fab' immunotoxin directed against mouse immunoglobulin. Only two antibodies, MEM75 and 120-2A3, both directed against the transferrin receptor (TfR) were predicted to form immunotoxins that would inhibit protein synthesis by the cells by 50% at a concentration (IC50) of 10(-8) M or less. This prediction was subsequently confirmed using several of the antibodies directly conjugated to ricin A-chain. By contrast, the same immunotoxins were highly toxic to non-myeloid cells which shared the target antigens. A comparison was made between the rates of endocytosis and degradation by HL60 cells of an anti-TfR immunotoxin 120-2A3.dgA, that was effective at killing myeloid cells, and a CD33 immunotoxin, p67-7.dgA, that bound to myeloid cells but did not kill them. The difference in potency of the two immunotoxins on HL60 cells was not due to deficient uptake of p67-7.dgA but was probably due to the more rapid intracellular degradation of p67-7.dgA. Fast and effective degradation in lysosomes, if a general finding, could explain the poor susceptibility of myeloid cells to ricin A-chain immunotoxins.

Animals↗
PubMed1990

Antitumor effects of ricin A chain immunotoxins prepared from intact antibodies and Fab' fragments on solid human Hodgkin's disease tumors in mice.

Three monoclonal antibodies which strongly bind to Hodgkin and Reed-Sternberg cells and two corresponding Fab' fragments were linked to deglycosylated ricin A chain (dg A) to evaluate their potential as immunotoxins for the treatment of Hodgkin's disease. Two of the antibodies, Ber-H2 and HRS-3, were shown to bind to the same epitope on the CD30 antigen, whereas the third antibody, IRac, bound to a different antigen. None of the antibodies significantly cross-reacted with normal human tissues as judged by indirect immunofluorescence and immunoperoxidase analyses on frozen sections from 28 normal tissues. All three antibodies formed potent and specific immunotoxins. They inhibited protein synthesis of the L540 Hodgkin's disease cell line in vitro by 50% at concentrations of 1 x 10(-11) M for IRac.dgA, 9 x 10(-11) M for HRS-3.dgA, and 2 x 10(-10) M for Ber-H2.dgA. HRS-3 Fab' and IRac Fab' immunotoxins were 7.8- and 60-fold less cytotoxic, respectively, than their intact counterparts in vitro. In vivo, a single i.v. injection of a dose of Ber-H2.dgA, HRS-3.dgA, or IRac.dgA corresponding to 40% of the LD50 induced lasting complete remissions in 38, 44, and 50%, respectively, of mice with solid s.c. L540 tumors of 60 to 80 mm3 size (0.5-cm diameter). At equivalent dosage (40% of the LD50), the HRS-3 Fab'.dgA and the IRac Fab'.dgA both induced lasting complete remissions in 25% of the mice, although the HRS-3 Fab'.dgA was significantly superior to IRac Fab'.dgA at retarding tumor growth in the remaining animals. The effectiveness of the immunotoxins depended on the size of the tumor at the time of injection, since IRac.dgA treatment induced complete remissions in 100% of mice with small tumors (10 to 20 mm3, approximately 0.3 cm in diameter) but only 13% of mice with larger tumors of 400 to 600 mm3 (approximately 1 cm in diameter). Tumors which regrew after IRac.dgA treatment mainly consisted of antigen-deficient mutants having reduced sensitivity to IRac.dgA but normal sensitivity to HRS-3.dgA. It is concluded that HRS-3.dgA, HRS-3 Fab'.dgA, and IRac.dgA are candidates for the treatment of Hodgkin's disease in humans.

Animals↗
PubMed1990

Evaluation of ricin A chain-containing immunotoxins directed against the CD30 antigen as potential reagents for the treatment of Hodgkin's disease.

Five monoclonal CD30 antibodies and two Fab' fragments were linked to deglycosylated ricin A chain (dgA), and their potential as immunotoxins for the treatment of Hodgkin's disease was evaluated. Cross-blocking experiments demonstrated that HRS-1, HRS-3, HRS-4, and Ber-H2 recognize the same epitope on the CD30 antigen and that Ki-1 binds to a different epitope. Scatchard analyses showed that HRS-3, HRS-4, and Ber-H2 bound strongly to L540 Hodgkin cells (Kd 15, 7, and 14 nM, respectively), whereas HRS-1 and Ki-1 bound more weakly (Kd 160 and 380 nM, respectively). The different affinities of the antibodies correlated closely with their cytotoxic potency as immunotoxins. HRS-3.dgA, HRS-4.dgA, and Ber-H2.dgA inhibited the protein synthesis of L540 cells by 50% at concentrations of 0.9-2.0 x 10(-10) M, whereas HRS-1.dgA and Ki-1.dgA were about 100 times less potent with 50% inhibitory concentrations of 0.8-1.0 x 10(-8) M. The most effective immunotoxins, HRS-3.dgA and HRS-4.dgA, were only 15 times less toxic than ricin itself. HRS-3 Fab'.dgA and HRS-4 Fab'.dgA were 7.8 and 3 times less potent than their IgG.dgA counterparts with 50% inhibitory concentrations of 7 x 10(-10) and 3 x 10(-10) M, respectively. Staining of human tissues revealed an unexpected cross-reactivity of HRS-4 with pancreatic cells of malignant and nonmalignant origin. HRS-1, HRS-3, Ber-H2, and Ki-1 showed very little cross-reactivity with any normal human tissues. It is concluded that HRS-3.dgA and HRS-3 Fab'.dgA are the immunotoxins of choice for in vivo therapy.

Antibodies, Monoclonal↗
PubMed1989

Neuronotoxic effects of monoclonal anti-Thy 1 antibody (OX7) coupled to the ribosome inactivating protein, saporin, as studied by suicide transport experiments in the rat.

As a first attempt to develop suicide transport agents based upon antineuronal antibodies, we studied an immunotoxin directed against the Thy 1 antigen which is on rat neurons. The immunotoxin was composed of mouse monoclonal anti-Thy 1 antibody (OX7) and the ribosome-inactivating protein, saporin, and was prepared using the heterobifunctional cross linker, SPDP, which provides a disulfide linkage between the two protein components. This immunotoxin reliably and selectively destroyed ipsilateral vagal motor and sensory neurons after injection into the cervical vagus. Injection of the immunotoxin into the caudate nucleus produced destruction of the ipsilateral substantia nigra, pars compacta and intralaminar thalamic nuclei (parafascicular and central median). Anti-mouse IgG immunoperoxidase staining confirmed axonal transport of OX7 by vagal sensory and motor neurons and by caudate afferents and efferents. Systemic toxicity was not observed with OX7-saporin. The neuronotoxic effects of OX7-saporin were specific since injections of a similarly constructed immunotoxin of irrelevant specificity or a mixture of OX7 and saporin were without suicide transport activity. These results show the feasibility of using immunotoxins as suicide transport agents.

Animals↗
PubMed1989

Pull-through approach to percutaneous angioplasty of totally occluded common iliac arteries.

A method has been developed to increase the probability of success of percutaneous transluminal balloon angioplasty of total occlusions of the common iliac artery when conventional methods have failed. In 10 patients with a totally obstructed iliac artery, a guide wire was passed through a catheter placed from the contralateral side around the aortic bifurcation and antegrade through the total obstruction. The end of the wire was either snared by a retrieval basket or guided through a sheath in the ipsilateral common femoral artery, thus providing a firmly anchored pathway for subsequent manipulations. Balloons were then inserted retrograde through both common femoral arteries and dilated. In the first five patients, ipsilateral retrograde passage of a guide wire had failed despite multiple attempts with a variety of devices. In the other five patients, the contralateral antegrade approach was used initially. The new method was successful in all 10 patients with totally obstructed common iliac arteries.

Angioplasty, Balloon↗
PubMed1988

Cavernous haemangioma presenting as an orbital mass after enucleation for a choroidal melanoma: case report.

A patient presented with an ipsilateral orbital mass four years after enucleation for a choroidal malignant melanoma. Clinical examination revealed a darkly coloured mass suggestive of recurrent melanoma. CT scanning indicated a locally extensive tumour. Management was by excision without resort to orbital exenteration. Pathological examination revealed a cavernous haemangioma. The natural history of this tumour is discussed.

Choroid Neoplasms↗
PubMed1985

Detection of an abdominal aneurysm by indium-111 platelet imaging.

The authors report a case in which In-111 platelet imaging provided uniquely useful information in the discovery of an abdominal aortic aneurysm. This case illustrates the potential usefulness of this procedure in the detection of unsuspected sites of thrombogenic vascular disease.

Aorta, Abdominal↗
PubMed1985

Selective sparing of enterochromaffin cells in graft versus host disease affecting the colonic mucosa.

Graft versus host disease affecting the large bowel causes destruction of the crypt epithelium. There is a selective sparing of enterochromaffin cells in the majority of cases. As a consequence, single as well as small clumps of enterochromaffin cells are to be seen in the sites formerly occupied by the destroyed crypt epithelium. The reason for this phenomenon is unclear, but it may be related to the fact that the enterochromaffin cells are end-stage and non-proliferating cells. This is useful diagnostically. However, cytotoxic drugs or irradiation must be excluded as the cause of the mucosal damage to bowel as there are theoretical reasons to expect that a similar phenomenon will be seen after these forms of therapy.

Adolescent↗
PubMed1983

An immunotoxin of ricin A chain conjugated to thyroglobulin selectively suppresses the antithyroglobulin autoantibody response.

The autoantigen thyroglobulin has been conjugated with the A chain of the toxin ricin. In vitro this conjugated "immunotoxin" specifically suppressed the thyroglobulin autoantibody response of lymphocytes from patients with Hashimoto's thyroiditis. Neither total immunoglobulin synthesis nor the synthesis of autoantibody to thyroid microsomes by these lymphocytes was affected by the immunotoxin. The demonstration that an autoantigen coupled to a toxin can induce specific immunological unresponsiveness suggests that such immunotoxins could provide a novel and highly selective means for deleting autoantibody-secreting lymphocyte clones in patients with autoimmune disease.

Antitoxins↗
PubMed1976

Rheumatoid arthritis treated with chlorambucil: a five-year follow-up.

The results of a five-year study of chlorambucil in patients suffering from rheumatoid arthritis are presented. The effect of treatment was to allow a reduction in corticosteroid dosage and a sustained remission of disease activity in patients. Three patients of the series of 22 developed neoplastic disease, and the signficance of this is discussed.

Acute Disease↗