Avapritinib-based SAR studies unveil a binding pocket in KIT and PDGFRA.

Avapritinib is the only potent and selective inhibitor approved for the treatment of D842V-mutant gastrointestinal stromal tumors (GIST), the most common primary mutation of the platelet-derived growth factor receptor α (PDGFRA). The approval was based on the NAVIGATOR trial, which revealed overall response rates of more than 90%. Despite this transformational activity, patients eventually progress, mostly due to acquired resistance mutations or following discontinuation due to neuro-cognitive side effects. These patients have no therapeutic alternative and face a dismal prognosis. Notable, little is known about this drug's binding mode and its medicinal chemistry development, which is instrumental for the development of the next generation of drugs. Against this background, we solve the crystal structures of avapritinib in complex with wild-type and mutant PDGFRA and stem cell factor receptor (KIT), which provide evidence and understanding of inhibitor binding and lead to the identification of a sub-pocket (Gα-pocket). We utilize this information to design, synthesize and characterize avapritinib derivatives for the determination of key pharmacophoric features to overcome drug resistance and limit potential blood-brain barrier penetration.

A new approach for probing the mobility and lifetime of photogenerated charge carriers in organic solar cells under real operating conditions.

A new transient charge extraction technique is presented, which facilitates simultaneous measurements of mobility and lifetime of photogenerated charge carriers in organic solar cells under real operating conditions. An adaptive field control is implemented keeping the solar cell at open circuit conditions during recombination. The practical benefit of the new technique is demonstrated by determining the mobility-lifetime parameter of solar cells based on PCDTBT:PC(71) BM and P3HT:PC(61) BM.

Synthesis of a cyanopeptide-analogue with trypsin activating properties.

An efficient synthesis of a peptidic analogue of cyanobacterial metabolites with proposed serine protease inhibitory activity has been developed. Surprisingly, one trypsin activating compound was obtained.

Biodistribution and dosimetry of indium-111-polyclonal IgG in normal subjects.

UNLABELLED: Indium-111-polyclonal IgG is a new imaging agent of infection and inflammation that has been developed as a possible replacement for radiolabeled leukocytes. We undertook a study to determine the safety, biodistribution and dosimetry of the agent in normal subjects. METHODS: Twelve normal male volunteers with an average age of 34 yr (range 21-55 yr) were studied. Each was injected with 1.22-1.47 mCi 111In-labeled polyclonal IgG; digital whole-body images, in addition to blood, urine and fecal samples, were obtained immediately after injection and at 6, 24, 48, 72, 96 and 120 hr. Whole-body counts, as well as individual organ data obtained by outlining regions of interest, were measured. Blood, urine and fecal counting were done in a well counter and compared to known standards; dosimetry calculations were performed with the MIRD technique. RESULTS: The mean whole-blood activity had a two-phase disappearance curve: the T1/2I was 11.4 hr (61.1%) and the T1/2II was 112.5 hr (38%). Twelve percent of the dose was excreted in the urine and 1.14% in the feces. Skeletal muscle had the highest percentage of uptake, followed by the bone marrow, liver and lungs; the spleen showed less than 1% uptake. Activity in the lungs varied with time, falling by 37% after 18 hr and by 68% after 72 hr. Dosimetry calculations indicated that the highest absorbed dose was to the liver (1.42 rad/mCi) followed by the testes (1.23 rad/mCi) and red marrow (0.976 rad/mCi). The total-body dose was 0.467 rad/mCi, with an effective dose equivalent of 790.84 mrem. CONCLUSION: The biodistribution of 111In IgG is similar to that of 99mTc-HMPAO-labeled leukocytes. Activity in the liver, kidneys and GI tract may make evaluation of infection in these regions difficult. The dosimetry data indicate that adequate doses can be administered for clinical imaging without exposing the patient to excessive radiation.

111-indium-DTPA-IgG lung imaging in patients with pulmonary and HIV infection.

111-Indium-DTPA-IgG (111In-IgG) is a new radiopharmaceutical that has been evaluated for the detection of infection without the need for in vitro cell labeling. We prospectively studied this agent in 33 patients suspected of having lung infections, most of whom also had HIV infection, and three patients with HIV infection and diarrhea without lung disease. Anterior and posterior lung images in the upright position were obtained within 24 h after intravenous administration of 2 mCi of 111In-IgG and were read in a blinded fashion by two nuclear medicine physicians. Of 29 patients suspected to have Pneumocystis carinii pneumonia (PCP), the diagnosis was confirmed by bronchoalveolar lavage in 18. Diffusely increased lung uptake of 111In-IgG was found in 17 of 18 patients who had PCP and was normal in 10 of 11 patients without PCP. The intensity of 111In-IgG uptake was related to sever gas exchange abnormality. Two patients with apparent bacterial lung infections had focal accumulation of 111In-IgG while two patients with minor radiographic abnormalities had no increased uptake. Normal lung uptake also occurred in two of three HIV-positive patients who had diarrhea and no lung disease. 111In-IgG appears to be useful in the detection of PCP and other pulmonary infections.

Indium-111 labelled pooled human immunoglobulin imaging to monitor the efficacy of specific therapy for Pneumocystis carinii pneumonia.

Functional imaging is ideally suited to monitoring the effect of specific therapy on disease processes. In this pilot study five patients with AIDS and Pneumocystis carinii pneumonia (PCP) were imaged with Indium-111 labelled pooled human immunoglobulin (111In-HIG) during infection and after therapy for PCP. The lung activity of 111In-HIG, measured as a lung/heart ratio, was calculated in a study performed during infection with PCP and after therapy. In all five patients the lung/heart ratio of 111In-HIG was reduced after treatment. The mean reduction in heart/lung ratio was 27% (range 12%-53%). If these results are confirmed by a larger study, 111In-HIG will be useful in monitoring the response of PCP to therapy in patients with AIDS.

The efficacy of indium-111-polyclonal IgG for the detection of infection and inflammation.

UNLABELLED: The purpose of this study was to determine the efficacy of 111In-polyclonal immunoglobulin (IgG) for the diagnosis of infection or inflammation. METHODS: Fifty-three patients with suspected infection were prospectively studied. Each underwent an 111In-polyclonal IgG study; biopsy, surgery, additional nuclear medicine scans and radiographic studies were used to confirm the IgG scan results. RESULTS: The polyclonal IgG scan had a sensitivity of 97.9% and a specificity of 94% for infection or inflammation. When only infection or severe inflammation such as bowel infarction was considered, the sensitivity remained the same but the specificity fell to 83%. Chronic infections were detected equally as well as acute infections. Antibiotics, steroids, anti-inflammatory agents, diabetes and diminished renal function did not affect scan sensitivity. There were no adverse reactions to the radiopharmaceutical. Three patients underwent extended imaging. Their scans stayed positive for an average of 8 days. Three patients treated for infection had their scans turn negative on repeat study, confirming the efficacy of their antibiotic therapy. CONCLUSION: Indium-111-polyclonal IgG is an effective imaging agent of infection and/or inflammation that is useful in a variety of infections and in severe inflammatory diseases. The ease of preparation and safety make it an attractive alternative to labeled leukocytes.

In vivo bioactivity and biodistribution of chemotactic peptide analogs in nonhuman primates.

The dose dependence of the effect of chemotactic peptide on peripheral leukocyte levels was measured in normal Rhesus monkeys. A 99mTc-labeled hydrazino nicotinamide (HYNIC) derivatized chemotactic peptide analog was used to study biodistribution and inflammation imaging in Rhesus monkeys. In normal animals the studies demonstrated that chemotactic peptide induced a clear dose-dependent reduction in peripheral leukocyte levels. The decrease in leukocyte number occurred almost immediately after injection and rapidly returned to baseline. Significant effects on differential WBC count, blood pressure, pulse rate or respiration rate were not detected. The lowest dose of peptide tested (10 ng/kg) had minimal effect on leukocyte level. The HYNIC derivatized peptide was prepared in excellent yield and purity, had biological activity similar to the native peptide and was readily labeled at specific activity of > 20,000 mCi/mumole. When approximately 0.5 mCi (< 2.0 ng/kg) of radiolabeled peptide was injected in monkeys with focal sites of mild sterile inflammation, a pattern of biodistribution similar to radiolabeled WBCs was observed and reductions in leukocyte levels were not detected. At 3 hr after injection, the site of inflammation was readily apparent with a target-to-background ratio of approximately 3:1. These studies demonstrate that radiolabeled chemotactic peptide analogs are effective agents for imaging sites of inflammation in monkeys. By radiolabeling at high specific activity, the effect of these reagents on peripheral leukocyte levels can be avoided.

Preparation and preliminary evaluation of technetium-99m-labeled fragment E1 for thrombus imaging.

Fragment E1 labeled with 123I has been previously shown to permit imaging of thrombi in patients within as little as 20 min after injection. Because of the relatively rapid localization and blood disappearance of this protein, 99mTc would be the most clinically acceptable radionuclide for labeling Fragment E1. In this study, human fragment E1 was derivatized with a hydrazino nicotinate function to permit radiolabeling with reduced technetium. The modification reaction was carried out while the fragment E1 was protected in a complex, so that the modification occurred in nonfunctional regions of the fragment E1 molecule. After radiolabeling with 99mTc, the modified fragment E1 retained its functional activity, as judged by its binding to fragment DD in vitro. The ability of 99mTc-fragment E1 to produce images of venous thrombi was demonstrated in animal models. Images were focally positive within 20 min to 1 hr after injection. Thrombus-to-blood ratios exceeded those from 125I-fibrinogen in the same animals. This method of labeling appears to provide an alternative radiolabel to 123I without compromising the function of fragment E1.

Clinical evaluation of a scintigraphic method for diagnosing inflammations/infections using indium-111-labeled nonspecific human IgG.

This study was undertaken as part of a Phase II study to assess the sensitivity and safety of 111In-DTPA-human IgG, an imaging agent for the detection of inflammations and/or infections. Forty patients with infection/inflammation on the basis of clinical findings, microbiologic results, and/or the basis of results from other imaging modalities were studied. For evaluation of sensitivity, whole-body images were obtained at 6-12 hr (early) and 20-28 hr (delayed) postinjection and occasionally at 48 hr. No adverse reactions were recorded in any of the 40 patients studied. Positive results were obtained in 37 of 37 evaluable subjects (100%). The test appears to be a promising method for the detection of inflammation and/or infection.

Preparation of hydrazino-modified proteins and their use for the synthesis of 99mTc-protein conjugates.

The syntheses and protein linking properties of succinimidyl 4-hydrazinobenzoate hydrochloride (SHBH) and succinimidyl 6-hydrazinonicotinate hydrochloride (SHNH), two new heterobifunctional linkers which lead to hydrazino-modified proteins, are described. SHBH-modified proteins are unstable due to the presence of the phenylhydrazine moiety. This problem was overcome by synthesizing the hydrazinopyridine analogue SHNH, and the conjugates derived from this linker are stable. Tc(V) oxo precursors readily add to hydrazinopyridine-modified proteins to yield the desired 99mTc-radiolabeled protein. 99mTc-hydrazinopyridine-polyclonal IgG conjugates are useful agents for the imaging of focal sites of infection.

Detection of focal infection by 111In-human polyclonal IgG.

Eleven patients with suspected foci of inflammation and/or infection were scanned with 111In-labeled polyclonal human IgG. Seven patients were suspected of having the source of their infection in the abdomen, three in the musculoskeletal system and one in the thoracic aorta. The test was truly positive in seven patients, truly negative in three and falsely negative in one. All the true positive cases showed abnormally increased radiopharmaceutical uptake at the site of infection by six hours, suggesting the diagnosis, although the intensity of uptake increased progressively 24 hours later. There were no untoward effects noted in this series. This examination is potentially useful in the early depiction of focal sources of infection/inflammation.

Laboratory tests in the differential diagnosis of hyperamylasemia.

We evaluated the clinical utility of some recently developed laboratory methods, including total amylase by three methods; isoamylase by inhibition and isoelectric focusing; lipase by pH-Stat and turbidimetry; and immunoreactive trypsin. All methods correlated highly positively with hyperamylasemia due to primary acute pancreatitis. Pancreatic-type isoamylase determinations have the greatest clinical usefulness, because total amylase, lipase, and immunoreactive trypsin are increased in a relatively high percentage of other abdominal diseases. Increases in the last-mentioned enzymes in nonpancreatic abdominal disease may be the result of injuries to the pancreas secondary to the primary disease, which are being detected with these highly sensitive methods. Because of the high clinical sensitivity of lipase and immunoreactive trypsin determinations, a normal result tends to exclude acute pancreatitis. Hyperamylasemia seen in lung carcinoma is due to increase in an amylase isoenzyme similar to the salivary-type amylase. The method for pancreatic-type isoamylase based on selective inhibition is satisfactory for routine clinical laboratory use.

Developmental aspects of hepatic glutathione S-transferase activities in male rats.

The postnatal development of glutathione S-transferase activities was investigated in post-microsomal supernatants of the livers of male rats. A period of up to the age of 200 days was covered, using styrene 7,8-oxide as the electrophilic substrate for the transferase. Activity in animals on the day of delivery was small but significantly above the level of spontaneous conjugation. During 5 weeks postpartum the specific activity increased regularly to about sixfold when expressed as per mg of cytosolic protein, thereafter the activity slightly decreased. During the 5th postnatal week a sudden decrease in activity was observed, but it returned to the original value within about 5 days. The effect of weaning on this phenomenon was studied by comparing weaned with non-weaned rats in an investigation of glutathione S-transferase maturation in the 4th and 5th week postpartum, using styrene 7,8-oxide and 1-chloro-2,4-dinitrobenzene as the electrophilic substrates. Weaned rats exhibited the decrease in activity only when styrene oxide was the substrate. It is concluded that glutathione S-transferase levels in rat liver are low at birth, and develop gradually during the first 5 postnatal weeks. Transferase activities towards styrene oxide and chlorodinitrobenzene appears to mature independently and are partly associated with weaning.