Evaluation of 99mTc-RP128 as a potential inflammation imaging agent: human dosimetry and first clinical results.

UNLABELLED: 99mTc-RP128 is a bifunctional peptide chelate designed to target the tuftsin receptor, expressed by neutrophils, monocytes, and macrophages. Studies in animal models of both infectious and noninfectious inflammation have shown a positive correlation between accumulation of 99mTc-RP128 and quantitative measures of inflammation. A phase 1 trial was conducted with the objective of determining the safety, biodistribution, and human dosimetry of 99mTc-RP128 in eight healthy volunteers. For evaluation of the potential of 99mTc-RP128 for imaging sites of inflammation, 10 patients with active rheumatoid arthritis were studied. METHODS: Normal biodistribution was determined using the conjugate view method up to 24 h after intravenous injection of 280 MBq 99mTc-RP128. Dosimetry calculations were based on standard MIRD methodology, using the International Commission on Radiological Protection model 30 of the gastrointestinal tract and a voiding bladder model with an interval of 4.8 h. For rheumatoid arthritis patients, whole-body scans and spot views of the hands, knees, and feet were obtained at 1 and 3 h after injection of 475 MBq 99mTc-RP128. RESULTS: 99mTc-RP128 was cleared rapidly from the blood by renal excretion, and no major organs showed significant accumulation. The synovia of the major joints were visualized for all subjects. The effective dose equivalent and the effective dose were calculated to be 0.011 and 0.0094 mSv/MBq, respectively. The highest dose was to the bladder wall, which received 0.076 mGy/MBq. In all rheumatoid arthritis patients, we observed a markedly increased uptake in several affected joints. Painful and swollen joints were detected with a sensitivity of 76% and 69%, respectively. Seventy-three percent of the joints with radiographic signs of erosion were scintigraphically positive. In some patients, lines of increased activity were observed and were considered to correspond to uptake in the synovium lining tendon sheaths in the wrists and hands. CONCLUSION: This study shows that 99mTc-RP128 is safe and can successfully be used to visualize clinically affected joints in patients with long-standing rheumatoid arthritis. A proposed radioactive dose of 450-500 MBq will produce an effective dose well within the range of effective doses for commonly used radiopharmaceuticals.

Survey of commercial airline pilots' hearing loss.

64 commercial airline pilots (ages 35-64 yr, Mdn: 53) were surveyed regarding hearing loss and tinnitus. Within specific age groups, the proportions responding positively exceed the corresponding proportions in the general population reported by the National Center for Health Statistics.

Imaging inflammation with 99Tcm-labeled chemotactic peptides: analogues with reduced neutropenia.

Two 99Tcm-labelled analogues of the chemotactic peptide ForMLF were evaluated as potential agents for imaging inflammation and infection, in the hope that they would be simple to use and would give diagnostically useful images shortly after injection. The peptides differed in the chelation site for 99Tcm and the presence of a hydrophilic spacer. The sequences of RP050 and RP056 were ForNleLFNleYK(G)G-C(Acm)-GPic and ForNleLFNleYKK(DG)GC(Acm)SPic respectively, where Pic is picolinic acid. In in vitro tests of binding to the ForMLF receptor on polymorphonuclear neutrophils and potency for release of myeloperoxidase, RP056 was similar in potency to ForMLF, whereas RP050 was 10 times more potent. When administered in 5-nmol doses to rats, RP050 produced less extensive neutropenia than ForMLF, whereas RP056 produced very little neutropenia. Following labelling by ligand exchange from tartrate or glucoheptonate at 100 degrees C and purification using a C-18 solid-phase extraction cartridge, 4-MBq doses were administered to rats bearing infectious (Escherichia coli) or sterile (zymosan) inflammation sites in the thigh. The inflammation-to-normal muscle ratios at 30 min after injection were 3.9 +/- 0.4 for RP050 and 4.7 +/- 0.3 for RP056 (mean +/- S.E.M., n = 4), and the ratios were maintained for up to 3 h. These peptides are promising agents for imaging inflammation and infection.

Differential coupling of subtypes of the muscarinic receptor to adenylate cyclase and phosphoinositide hydrolysis in the longitudinal muscle of the rat ileum.

The binding affinities of selective muscarinic antagonists were compared with their ability to block receptor-mediated inhibition of adenylate cyclase and stimulation of phosphoinositide hydrolysis in the longitudinal muscle of the rat ileum. When measured by competitive inhibition of the binding of N-[3H]methylscopolamine, the binding properties of selective muscarinic antagonists were consistent with a two-site model. Approximately 84% of the binding sites (major sites) had high affinity for the M2-selective antagonists methoctramine and AF-DX 116 (11[[2-[(diethylamino)methyl]-1- piperidinyl]acetyl]-5,11-dihydro-6H-pyrido [2,3-b][1,4]benzodiazepine-6-one), whereas the remainder of the sites (minor sites) had high affinity for hexahydrosiladifenidol and its para-fluoro derivative. There was good agreement between the estimates of the dissociation constants of muscarinic antagonists for the major binding site and those measured by antagonism of the adenylate cyclase response. There was also good agreement between the dissociation constants of muscarinic antagonists for the minor binding site and those measured by antagonism of the phosphoinositide response and the contractile response. Our data indicate that there are at least two types of muscarinic receptors in the longitudinal muscle of the ileum, the more abundant being an M2 receptor, which mediates an inhibition of adenylate cyclase activity, and the less abundant being an M3 receptor, which triggers contraction and phosphoinositide hydrolysis.

Incidence of response and long-term follow-up in patients with hairy cell leukemia treated with recombinant interferon alfa-2a.

Thirty-five evaluable patients with hairy cell leukemia (HCL) were treated with recombinant interferon alfa-2a (rIFN-alpha 2a), given at a dose of 3 X 10(6) units (U) intramuscularly (IM) daily for 6 months followed by 3 X 10(6) U IM three times a week for an additional 18 months in a single institution study. All treatment was stopped after 24 months. Sixty-nine percent of patients achieved a partial response, 11% a minor response, and 3% (one patient) had stable disease. Six patients (17%) did not respond to rIFN-alpha 2a. Two patients (6%) achieved a response but later progressed on treatment. A total of 23 patients completed 2 years of treatment and are evaluable for long-term follow-up at a median of 20 months postcompletion of therapy (range 9 to 32 months). Eleven patients (48%) have had progression of their disease at a median of 10 months (range .5 to 25 months) after treatment was discontinued. Statistical analysis of pretreatment patient characteristics did not reveal any factor(s) associated with a high probability of responding to rIFN-alpha 2a; however, analysis of post-treatment variables measured after 2 years of treatment suggested that a low platelet count was associated with a high rate of disease progression. These findings are compared with other published trials using rIFN-alpha 2b, a similar but not identical rIFN preparation. We conclude that while rIFN-alpha 2a has a high overall response incidence, the rate of disease progression after therapy is discontinued approaches 50%, and that a subset of patients can be identified who are at high risk for recurrence after completing 2 years of treatment.

Incidence and clinical significance of neutralizing antibodies in patients receiving recombinant interferon-alpha 2a.

In clinical trials with a range of doses of recombinant interferon-alpha 2a, we observed a 25% overall incidence of neutralizing antibody development. Careful data analysis did not reveal a relationship between antibody development and therapeutic response. Of 752 patients evaluable for antibody development and clinical response, 31% of the antibody-positive patients and 28% of the antibody-negative patients had therapeutic responses. Although the formation of anti-IFN antibodies seems to be associated with most IFN preparations, incidence and clinical significance have been difficult to determine for a number of reasons. Different assays with differing sensitivities for the detection of IFN antibodies have been utilized in different studies. Additionally, important clinical variables that affect antibody development have often not been carefully controlled or analyzed. The relationship between antibody development and multiple related factors, such as route of administration, dose regimen, cumulative dose, duration of treatment, and the underlying disease, requires clarification. Initial analyses suggest that the median time to antibody development may vary with the dose regime and cumulative dose, as well as the route of administration. Carefully designed prospective studies controlling for influential clinical variables and utilizing standardized assay techniques are required for a meaningful analysis of the antigenic potential of all therapeutic protein products.