Impact of Long-Term Exposure to the Tyrosine Kinase Inhibitor Imatinib on the Skeleton of Growing Rats

<div><p>The tyrosine kinase (TK) inhibitor imatinib provides a highly effective therapy for chronic myeloid leukemia (CML) via inhibition of the oncogenic TK BCR-ABL1. However, off-target TKs like platelet-derived growth factor receptors (PDGF-R) and colony-stimulating factor-1 receptor (c-fms), involved in bone remodeling, are also inhibited. Thus, pediatric patients with CML on imatinib exhibit altered bone metabolism, leading to linear growth failure. As TKI treatment might be necessary for a lifetime, long-term effects exerted on bone in children are of major concern. Therefore, we studied the skeletal long-term effects of continuous and intermittent imatinib exposure in a juvenile rat model.</p><p>Four-weeks-old male Wistar rats were chronically exposed to imatinib via drinking water over a period of 10 weeks. Animals were exposed to a standard and high imatinib dosage continuously and to the high imatinib dose intermittently. Bone mass and strength were assessed using pQCT, micro-computed tomography (μCT), and biomechanical testing at the prepubertal, pubertal, and postpubertal age. Bone length and vertebral height as well as biochemical markers of bone turnover were analyzed.</p><p>Femoral and tibial bone length were dose-dependently reduced by up to 24% (p<0.0001), femoral and tibial trabecular bone mass density (BMD) were reduced by up to 25% (p<0.01), and femoral breaking strength was lowered by up to 20% (p<0.05). Intermittent exposure mitigated these skeletal effects. Long-term exposure resulted in reduced vertebral height by 15% and lower trabecular BMD by 5%. Skeletal changes were associated with suppressed serum osteocalcin (p<0.01) and non-significantly elevated serum CTX-I and PINP levels.</p><p>In conclusion, imatinib mainly impaired longitudinal growth of long bones rather than the vertebrae of growing rats. Interestingly, intermittent imatinib exposure has less skeletal side effects, which may be beneficial in pediatric patients taking imatinib.</p></div

Femoral BV/TV, Tb.Th, Tb.N, and Tb.C during long-term imatinib exposure.

<p>Three dimensional trabecular microarchitecture of the right femora was assessed by μCT. Trabecular region of interest was defined manually located within the secondary spongiosa in prepubertal femora 196 slices, pubertal femora 226 slices, and in postpubertal femora 256 slices. For trabecular bone regions, bone volume/ total volume (BV/TV), trabecular thickness (Tb.Th), trabecular number (Tb.N), and trabecular connectivity (Tb.C) were calculated. Data represents mean ± 95% CI. Prepubertal = age of rats: 6 weeks, duration of exposure: 2 weeks (n = 4 each group); Pubertal = age of rats: 8 weeks, duration of exposure: 4 weeks (n = 3 each group); Postpubertal = age of rats: 14 weeks, duration of exposure: 10 weeks (n = 3 each group). Statistical analysis at defined time points: * p<0.05 versus age-related controls; ** p<0.01 versus age-related controls; *** p<0.001 versus age-related controls.</p

Bone length, total BMD, trabecular BMD, and cortical BMD of the femora (A), tibiae (B), and vertebra L2 (C) during long-term imatinib exposure assessed by pQCT.

<p>BMD = bone mineral density; Prep = prepubertal (age of rats: 6 weeks, duration of exposure: 2 weeks; n = 10 each group); Pub = pubertal (age of rats: 8 weeks, duration of exposure: 4 weeks; n = 8 each group); Postpub = postpubertal (age of rats: 14 weeks, duration of exposure: 10 weeks; n = 8 each group); Data represents mean ± 95% CI. Statistical analysis at defined time points: * p<0.05 versus age-related controls; ** p<0.01 versus age-related controls; *** p<0.001 versus age-related controls.</p

Fluid intake of the rats during long-term imatinib exposure.

<p>Fluid intake was measured 3 times weekly (Monday, Wednesday, Friday). Data represents mean ± 95% CI.</p

DataSheet_1_Patient-reported long-term outcome following allogeneic hematopoietic stem cell transplantation in pediatric chronic myeloid leukemia.pdf

BackgroundPediatric CML is very rare. Before the introduction of tyrosine kinase inhibitors (TKIs), allogeneic hematopoietic stem cell transplantation (HSCT) from a donor -if available- was the standard cure attempt. Data on the long-term outcome and health-related quality of life (HRQOL) in former pediatric CML patients undergoing HSCT are lacking.Study questionWe investigated long-term survivors’ self-reporting to a questionnaire sent out to patients formerly enrolled in pediatric CML-HSCT trials.MethodsIndividuals with CML transplanted at age Results111/171 (64.9%) individuals survived HSCT long-term and 86/111 (77.5%) fulfilled all inclusion criteria and received the questionnaire. 37/86 (43%) participants (24 female, 13 male, median age at HSCT 12 years [range 2-18], median age at the time of the survey 29 years [range 18-43]) responded after a median follow-up period of 19 years (range 4-27) after HSCT. 10/37 (27%) participants underwent no regular medical follow-up examinations. Self-reported symptoms like chronic graft-versus-host disease (cGvHD)-associated organ impairments and conditioning regimen consequences could causatively not sharply be separated in each case. Complains comprised hypothyroidism (N=11, 30%), infertility (N=9, 24%), lung problems, dry eyes (each N=7, 19%), skin alterations (N=6, 17%), hair problems (N=4, 11%), and sexual dysfunction (N=3, 9%). 10 (27%) participants experienced 13 CML relapses after a median interval from HSCT of 31 months (range 2-93). Only one patient underwent 2nd SCT after failure of relapse treatment with TKIs. Six secondary malignancies (dysplastic melanocytic nevus and ALL, basal cell carcinoma (N=2), rhabdomyosarcoma, and thyroid carcinoma developed in 5 (13%) participants. As assessed by the SF-36 questionnaire, impaired physical health was mainly associated with cGvHD. The mental component summary score showed that also participants without cGvHD scored significantly lower than the general population. When assessed by the FACT-BMT, participants with cGvHD scored significantly lower while participants without cGvHD scored even 5 points higher than the data from controls. 18 (49%) participants considered the sequelae of HSCT an obstacle to education. Out of the total cohort, N=20 (54%), N=7 (19%), N=5 (14%), and N=4 (11%) participants worked full time, part-time, were unemployed, or had not yet finalized their education, respectively. 20 (54%) participants lived as singles, 8 (22%) lived in a partnership, 6 (16%) were married, and 3 (8%) had been divorced. Four (11%) participants reported a total number of 7 children.ConclusionThis first assessment of HRQOL in former pediatric patients with CML surviving HSCT for more than two decades demonstrates self-reported satisfactory well-being only in the absence of cGvHD. Research-based on self-reported outcomes sheds light on former patients’ perspectives and provides an additional layer of valuable knowledge for pediatric and adult hematologists. Regular follow-up examinations are mandatory helping to avoid that late secondary neoplasias, CML-relapse, and disorders forming the broad range of possible long-term consequences of HSCT are not detected too late.</p

Olfactory bulb volumes.

*<p>two-tailed = 0.179.</p

Smaller volumes of subcortical structures in ALL-subjects compared to controls as revealed by FIRST analysis.

*<p>two-tailed.</p>*<p>P<0.05 two-tailed.</p

Demographics of ALL-survivors and non-exposed, healthy controls (N/A = non applicable, SD = standard deviation).

<p>Demographics of ALL-survivors and non-exposed, healthy controls (N/A = non applicable, SD = standard deviation).</p

Results of neuropsychological testing.

<p><i>Note.</i> CFT 20-R = Culture Fair Intelligence Test 20-R. CPT = Continous Performance Test. LGT-3 = German learning and memory test “Lern- und Gedächtnistest”.</p

Results from olfactory function tests.

*<p>two-tailed.</p