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K Hoekman

Publications and source records attributed to K Hoekman.

80 records · Page 5Linked to original sources
PubMed1989

Application of an in vitro model and a clinical protocol in the assessment of the potency of a new bisphosphonate.

The development of new bisphosphonates for clinical use requires congruence between the results of basic and clinical investigations. We have previously shown that this can be achieved with the use of an in vitro coculture mouse metacarpal resorption system sensitive to the activation of osteoclast precursors together with a clinical protocol in which the rate of decrease in urinary hydroxyproline excess with bisphosphonate treatment is assessed in patients with Paget's disease. In these studies bisphosphonates of known potencies were used. In the present study we have evaluated these approaches prospectively in the assessment of the antiresorptive potency of the new bisphosphonate (3-dimethylamino-1-hydroxypropylidene)-1,1-bisphosphonate (dimethyl-APD). A total of 42 patients with Paget's disease of bone received dimethyl-APD in doses predicted from the in vitro system. A total of 24 patients received the bisphosphonate intravenously (2, 4, and 8 mg/day) in groups of 8 patients each and 18 orally (100, 200, and 400 mg/day) in groups of 6 patients each for 10 days. Dimethyl-APD therapy was highly effective in inhibiting bone resorption. Urinary hydroxyproline excretion reached 30.9 +/- 5.6, 17.1 +/- 3.1, and 2.1 +/- 5.3% of initial excess after 10 days treatment with intravenous dimethyl-APD, 2, 4, and 8 mg/day, and 37.4 +/- 18, 10.4 +/- 8.5, and 13 +/- 4.1% with oral therapy, 100, 200, and 400 mg/day, respectively. Comparison of the antiresorptive potency of dimethyl-APD with that of APD showed that the former is roughly five times more potent, as predicted in the in vitro study.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1985

Characteristics and bisphosphonate treatment of a patient with juvenile osteoporosis.

We studied a 13 1/2-yr-old boy with severe juvenile osteoporosis and multiple metaphyseal and vertebral fractures. Biochemically, there was evidence of non-PTH mediated excessive bone resorption, low intestinal calcium absorption, and a strikingly negative calcium balance. He was treated with (3-amino-1-hydroxypropylidene)-1,1-bisphosphonate, a bisphosphonate capable of inhibiting bone resorption rapidly, and had dramatic clinical and biochemical improvement. All indices of resorption were normal within a week after initiation of therapy and his 1,25-dihydroxyvitamin D concentration, which was only 9.6 pg/ml before treatment, rose to 62.4 pg/ml. These changes were associated with an increase in calcium absorption and positive calcium balance. Radiological improvement with healing of metaphyseal and one diaphyseal fractures and signs of sclerosis near the growth plates of the affected metaphyses and at the end plates of the vertebrae also occurred. (3-Amino-1-hydroxypropylidene)-1,1-bisphosphonate, therefore, with its rapid suppression of resorption and the accompanying hormonal changes, is a very effective treatment for juvenile osteoporosis. The primary defect of this obscure syndrome seems to be uncontrolled activity of metaphyseal osteoclasts; disturbances of vitamin D metabolism and of intestinal calcium absorption are secondary events.

Adolescent↗
PubMed1984

Acute leukemia following therapy for teratoma.

Three cases of acute leukemia are reported following aggressive therapy for inoperable germ cell tumors. Two patients were treated by radiation plus cytotoxic chemotherapy and the third received only drugs. The time between onset of these therapies to death from leukemia was 4, 17 and 61 months.

Acute Disease↗
PubMedDate not supplied

SU6668, a multitargeted angiogenesis inhibitor.

Angiogenesis plays a critical role in the growth and metastasis of solid and hematologic malignancies. This complex and highly regulated process involves numerous different cell types and mediators. Vascular endothelial growth factor, basic fibroblast growth factor, and platelet-derived growth factor are among the soluble factors that stimulate this process. They are ligands for specific tyrosine kinase receptors that are important in transduction of intracellular signals and induction of angiogenesis. SU6668 is a novel molecule that competitively inhibits the tyrosine kinase of the receptors for vascular endothelial growth factor, basic fibroblast growth factor, platelet-derived growth factor, and c-kit. In vitro studies have confirmed that SU6668 inhibits growth factor-stimulated tyrosine phosphorylation. SU6668 also has significant antitumor activity against many types of tumor xenograft explants in athymic mice. SU6668 inhibits angiogenesis through several mechanisms, including the induction of apoptosis in vascular endothelial cells and tumor cells. Currently, Phase 1 studies are being initiated to evaluate the potential of SU6668 as an anticancer agent for humans.

Angiogenesis Inhibitors↗