A phase I study of samarium-153 ethylenediaminetetramethylene phosphonate therapy for disseminated skeletal metastases.

Thirty-five patients with disseminated skeletal metastases from a variety of tumor types underwent clinical trial of samarium-153 ethylenediaminetetramethylene phosphonate (153Sm-EDTMP) on a day-patient basis. Individual beta radiation dosimetry was based on pharmacokinetic studies of a 20 mCi tracer dose of 153Sm-EDTMP. The retained skeletal activity varied unpredictably from 40% to 95% of the administered dose, but in all patients greater than 98% of the nonosseous activity was cleared in the urine within 6 hours. Prospective calculation of radiation dosimetry in each patient permitted an accurate dosage schedule based upon total red marrow exposure, starting at 100 cGy and escalating to 280 cGy to define the dose-limiting myelotoxicity. Pain was relieved in 22 of 34 evaluable patients (65%) for periods ranging from 4 to 35 weeks, following a single administration of 153Sm-EDTMP. Recurrence of pain responded to retreatment with 153Sm-EDTMP in five of nine patients. The dose-limiting toxicity was myelosuppression manifested particularly by delayed thrombocytopenia. Platelet counts less than 100 x 10(9)/L occurred in 42% of courses when bone marrow radiation absorbed dose exceeded 200 cGy. Myelosuppression was transient and platelet counts had recovered to pretreatment levels within 10 weeks of treatment. 153Sm-EDTMP is effective for the amelioration of pain due to disseminated skeletal metastases particularly with carcinoma of breast or prostate where 83% of patients experienced pain relief. In 15 of the 34 evaluable patients there was evidence of stabilization or regression of skeletal metastases on radiographs and follow-up technetium-99m methylene diphosphonate (99mTc-MDP) bone scans.

Labeling of monoclonal antibodies with samarium-153 for combined radioimmunoscintigraphy and radioimmunotherapy.

The labeling of a monoclonal antibody K-1-21 with 153Sm has been investigated using the bifunctional chelate cyclic diethylenetriaminepentaacetic acid (DTPA) anhydride. Labeling efficiencies greater than 60% were obtained using high specific activity [153Sm]chloride and a cDTPAa:MAb conjugation ratio of 20:1. The resultant labeled antibody had a s.a. greater than 150 MBq.mg-1 and a % retained immunoreactivity greater than 90%. Imaging and biodistribution studies in a rat model demonstrated that specific uptake of 153Sm-K-1-21 into s.c. implants of the target antigen could be clearly detected in scintigrams at 6 days p.i. The specific uptake (1.90 +/- 0.45% ID/g, 19.95 +/- 2.20 Implant:Blood ratio) compared favorably to 131I- and 111In-labeled K-1-21 (2.52 +/- 0.20 and 3.33 +/- 0.20% ID/g, 7.69 +/- 0.45 and 10.10 +/- 0.60 I:B, respectively). Labeling of MAbs with 153Sm for combined scintigraphy/therapy is feasible at clinically appropriate specific activities using cDTPAa, with the resultant conjugates retaining immunoreactivity and in vivo antigen localization.

Samarium-153 EDTMP therapy of disseminated skeletal metastasis.

153Sm-EDTMP (ethylenediaminetetramethylene phosphonate), prepared from a kit, was administered to 28 patients in a clinical trial of therapy for painful skeletal metastases unresponsive to all conventional treatment. The 103 keV gamma emission of 153Sm was utilized for prospective individual estimation of beta radiation absorbed dose to red marrow to minimize myelotoxicity and provide optimum internal radiotherapy to skeletal metastases in each patient. Pain relief occurred within 14 days of administration of 153Sm-EDTMP in 15 of 19 patients (79%) who could be evaluated at 6 weeks, when clinical response was maximal. Duration of response ranged from 4 to 35 weeks. Recurrence of pain responded to retreatment with 153Sm-EDTMP in five of eight cases. No dose-response relationship was apparent for pain relief but reversible myelotoxicity was frequently observed at radiation absorbed doses to bone marrow greater than or equal to 270 cGy. Dosimetry calculation was based on pharmacokinetic studies of a tracer administration of 153Sm-EDTMP in each patient. Assumptions inherent in this prospective method of predicting dose to bone marrow were validated experimentally. Biodistribution studies in rats demonstrated rapid skeletal uptake and long term retention of 153Sm-EDTMP in bone over 5 days. Urinary clearance accounted for 40% of injected dose, and less than 1.0% of administered activity was retained in non osseous tissue. Microdensitometry of autoradiographs of sheep vertebra and femur confirmed surface uptake of 153Sm-EDTMP in cortical bone and demonstrated relatively high trabecular bone activity which is the major component of radiation absorbed dose to bone marrow. Haematological studies in rabbits showed 153Sm-EDTMP-induced myelotoxicity to be transient and no histopathological abnormalities were demonstrable with doses ten times greater than those administered to patients.

Cloning and physical characterization of katE and katF required for catalase HPII expression in Escherichia coli.

Two genes, katE and katF, affecting the synthesis of catalase HPII in Escherichia coli, have been cloned. The multistep cloning protocol involved: screening for the tet gene in a transposon interrupting the genes, selecting DNA adjacent to the transposon, and using it to probe a library of wild-type DNA to select clones from which katE and katF were subcloned into pAT153. The clones were physically characterized and the presence of the genes confirmed by complementation of their respective mutations. The location of the transposon insertions in the two genes was determined by Southern blotting of genomic digests to further confirm the identity of the cloned genes. A 93-kDa protein, the same size as the subunit of HPII, was encoded by the katE plasmid, indicating that katE was the structural gene for HPII. A 44-kDa protein was encoded by the katF plasmid.

Nucleotide sequence of katG, encoding catalase HPI of Escherichia coli.

The gene katG, encoding catalase HPI of Escherichia coli, was sequenced, predicting a 726-amino-acid protein. The sequence was confirmed by identification of potential regulatory elements and amino acid sequencing of peptides. HPI shows no homology to other catalases. The distances between katG, metF, and ppc were defined.

Samarium-153 chelate localization in malignant melanoma.

153Sm, a radiolanthanide of half life 46.27 h, has a gamma emission of 0.103 MeV which is well suited to imaging, it is also a moderate energy beta emitter and tumour localization of various 153Sm chelates was evaluated in B16 murine melanoma to assess their endoradiotherapeutic potential. 153Sm was prepared from enriched 152Sm in the Australian Nuclear Science and Technology Organization reactor. 153Sm chelates were prepared from 153Sm-chloride and their chromatographic behaviour characterized. Tumour and organ uptake of 153Sm-chloride, 153Sm-citrate and the 153Sm chelates, DTPA, HEDTA, HIDA, BZ, PBH, PIH and NTA were measured at 1, 6, 24 and 48 h after intravenous administration to C57 black mice bearing either melanotic or amelanotic B16 melanoma of mean size 0.75 cm3. Histopathological examination of the tumours at each passaging assured comparability of the degree of melanogenesis and the absence of necrosis. 153Sm-chloride was immobile on chromatography and the rapid hepatic accumulation of both 153Sm-chloride and 153Sm-citrate was attributed to in vivo formation of a colloid. In contrast, 153Sm-DTPA, moving at the solvent front on chromatography, showed no reticuloendothelial accumulation in vivo and was rapidly excreted by the kidneys without tumour uptake. The other 153Sm chelates were of intermediate stability and all localized in both melanotic and amelanotic tumours, although to a significantly lesser degree than 67Ga-citrate. The relatively high 153Sm-HIDA activity in liver and 153Sm-NTA activity in bone impaired tumour definition, but on imaging of all the 153Sm chelates only 153Sm-DTPA failed to demonstrate the B16 melanoma and the best tumour delineation was obtained using 153Sm-HEDTA.

The preparation of high specific activity copper-64 for medical diagnosis.

The specific activity of 64Cu produced by the neutron irradiation of copper is too low to be used in some in vitro tests for metabolic diagnosis. This report describes the use of the Szilard-Chalmers reaction to increase the specific activity to useful levels.