Oral tetrahydrouridine and decitabine for non-cytotoxic epigenetic gene regulation in sickle cell disease: A randomized phase 1 study

BACKGROUND

Sickle cell disease (SCD), a congenital hemolytic anemia that exacts terrible global morbidity and mortality, is driven by polymerization of mutated sickle hemoglobin (HbS) in red blood cells (RBCs). Fetal hemoglobin (HbF) interferes with this polymerization, but HbF is epigenetically silenced from infancy onward by DNA methyltransferase 1 (DNMT1).

METHODS AND FINDINGS

To pharmacologically re-induce HbF by DNMT1 inhibition, this first-in-human clinical trial (NCT01685515) combined 2 small molecules-decitabine to deplete DNMT1 and tetrahydrouridine (THU) to inhibit cytidine deaminase (CDA), the enzyme that otherwise rapidly deaminates/inactivates decitabine, severely limiting its half-life, tissue distribution, and oral bioavailability. Oral decitabine doses, administered after oral THU 10 mg/kg, were escalated from a very low starting level (0.01, 0.02, 0.04, 0.08, or 0.16 mg/kg) to identify minimal doses active in depleting DNMT1 without cytotoxicity. Patients were SCD adults at risk of early death despite standard-of-care, randomized 3:2 to THU-decitabine versus placebo in 5 cohorts of 5 patients treated 2X/week for 8 weeks, with 4 weeks of follow-up. The primary endpoint was ≥ grade 3 non-hematologic toxicity. This endpoint was not triggered, and adverse events (AEs) were not significantly different in THU-decitabine-versus placebo-treated patients. At the decitabine 0.16 mg/kg dose, plasma concentrations peaked at approximately 50 nM (Cmax) and remained elevated for several hours. This dose decreased DNMT1 protein in peripheral blood mononuclear cells by >75% and repetitive element CpG methylation by approximately 10%, and increased HbF by 4%-9% (P < 0.001), doubling fetal hemoglobin-enriched red blood cells (F-cells) up to approximately 80% of total RBCs. Total hemoglobin increased by 1.2-1.9 g/dL (P = 0.01) as reticulocytes simultaneously decreased; that is, better quality and efficiency of HbF-enriched erythropoiesis elevated hemoglobin using fewer reticulocytes. Also indicating better RBC quality, biomarkers of hemolysis, thrombophilia, and inflammation (LDH, bilirubin, D-dimer, C-reactive protein [CRP]) improved. As expected with non-cytotoxic DNMT1-depletion, platelets increased and neutrophils concurrently decreased, but not to an extent requiring treatment holds. As an early phase study, limitations include small patient numbers at each dose level and narrow capacity to evaluate clinical benefits.

CONCLUSION

Administration of oral THU-decitabine to patients with SCD was safe in this study and, by targeting DNMT1, upregulated HbF in RBCs. Further studies should investigate clinical benefits and potential harms not identified to date.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT01685515.

Standard clinical practice underestimates the role and significance of erythropoietin deficiency in sickle cell disease

In sickle cell disease (SCD), vigorous reticulocytosis is required to partially compensate for chronic hemolytic anaemia. Consequently, early renal damage, insufficient to cause azotemia but sufficient to cause erythropoietin deficiency and chronic relative reticulocytopenia (chRR), could have severe clinical consequences. chRR was defined as reticulocytes <250×10(9) /l despite haemoglobin <9 g/dl on ≥ two occasions ≥4 weeks apart. The influence of multiple variables including chRR on time from first clinic visit to death was evaluated in 306 SCD patients. In univariate analyses, fetal haemoglobin, indices of renal damage (serum creatinine, proteinuria), chRR and age, were associated with rate of death. In multivariate analysis, only age and chRR (Hazard ratio 3·6, 95% CI 2·049-6·327, P<0·0001) were significant, underlining that chRR could be an early and important clinical consequence of renal damage. Even in chRR patients with normal serum creatinine levels, low haemoglobin and low reticulocyte counts were associated with low erythropoietin levels. In the general population, evaluation of erythropoietin levels is prompted by the combination of anaemia and abnormal serum creatinine. In SCD patients, this standard approach can miss a substantial risk factor for early death. chRR could be a practical and important criterion for diagnosis of erythropoietin deficiency in SCD.

Radioimmunoscintigraphy for postprostatectomy radiotherapy: analysis of toxicity and biochemical control

Our goal was to evaluate the role of radioimmunoscintigraphy (RIS) directed against prostate-specific membrane antigen (PSMA) in influencing postprostatectomy radiotherapy (RT) toxicity and biochemical control.

METHODS

The records of 107 postprostatectomy RT patients were reviewed. The group for whom no RIS scan was obtained (group A, n = 54) was identified as was the group for whom a RIS scan was obtained (group B, n = 53). Group B was further subdivided into those who had a RIS and CT-scan correlation to aid in treatment planning (subgroup B1, n = 40) versus those who did not (subgroup B2, n = 13). Gastrointestinal (GI) and genitourinary (GU) toxicities were reviewed for each of these groups and subgroups and compared. Biochemical failures (defined as 2 successive PSA rises after a nadir of >or=0.2 ng/mL) were identified to generate biochemical failure-free survival (BFFS) curves for each of the groups and subgroups.

RESULTS

No significant differences in late toxicity were observed between any group or subgroup. However, acute GI toxicity was higher in group B versus group A (P = 0.026), and acute GU toxicity was higher in subgroup B2 versus subgroup B1 (P = 0.050). Overall, most toxicity was grade 1 or 2; only one case of grade 3 toxicity and no cases of grade 4 or 5 toxicity were observed. Three-year BFFS was higher for group B versus group A (80.7% vs. 75.5%) and for subgroup B1 versus subgroup B2 (84.5% vs. 71.6%). On multivariate analysis of pretreatment (age, race), surgical/staging (stage, grade, margin status, extracapsular extension, lymph node status, seminal vesicle invasion, post-radical retropubic prostatectomy [RRP] prostate-specific antigen [PSA] nadir, maximum post-RRP PSA, and RRP-to-RT interval), and treatment (hormone therapy, RT dose, RT technique, RIS scan, and RIS/CT correlation) factors on BFFS, the only covariate reaching significance was RIS/CT correlation (P = 0.042).

CONCLUSION

A small BFFS advantage was observed in patients for whom RIS was used to guide RT decision making and treatment planning; however, this advantage only reached significance in this study for those for whom the RIS/CT correlation was used to guide target definition. The improved PSA control using RIS was achieved with a small increase in acute toxicity but with no observed change in late toxicity. These findings can serve as the basis for prospective studies in this area of investigation.

Analysis of Prostate-Specific Antigen Rebound Interval in Patients with Prostate Cancer Receiving Hormonal Therapy and External-Beam Radiation Therapy

The goal of this investigation is to characterize the clinical significance of the rebound interval (RI) after neoadjuvant short-course hormonal therapy (HT) and external-beam radiation therapy (RT), during which the prostate-specific antigen (PSA) may rise because of hormone withdrawal prior to full RT efficacy. The charts of 257 consecutive patients with localized prostate cancer who received short-course neoadjuvant HT and RT were reviewed. A piecewise-linear log PSA versus time curve was generated for each patient and averaged over the population to facilitate identification of the RI start and end dates. Existing definitions of biochemical failure--American Society for Therapeutic Radiology and Oncology (ASTRO), Vancouver and Houston--were applied, as were these same definitions modified to exclude failures during the RI. Sensitivity and specificity were analyzed, using no evidence (by digital rectal examination or radiology) of disease failure as the gold standard. The 5-year biochemical survival with different failure definitions were ASTRO versus ASTRO-modified: 81.6% versus 86.7%; Houston versus Houston-modified: 71.4% versus 76.7%; and Vancouver versus Vancouver-modified: 83.5% versus 85.6%. The sensitivity and specificity comparisons were ASTRO versus ASTRO-modified 58.3% versus 33.3%; 91.4% versus 94.3%, Vancouver versus Vancouver-modified: 50% versus 50%; 92.7% versus 95.5%, Houston versus Houston-modified: 100% versus 66.7%; 90.6% versus 92.2%. The RI after HT and RT is likely not merely an artifact of hormone withdrawal but is correlated with ultimate clinical outcome. Excluding RI failures can marginally improve specificity but may possibly have an unacceptable risk of lowering sensitivity. Further work is needed to design and validate definitions of failure, which account for the RI.

Influence of radioimmunoscintigraphy on postprostatectomy radiotherapy treatment decision making

The aim of this study was to evaluate the role of radioimmunoscintigraphy (RIS) directed against prostate-specific membrane antigen (PSMA) in influencing postradical retropubic prostatectomy (RRP) radiotherapy (RT) decision making.

METHODS

The records of consecutive patients who underwent RRP, who were referred for consideration of RT, and for whom an RIS scan was obtained were reviewed. The RT decisions, with regard to (a) the decision to offer RT and (b) the general volume to be treated [prostate fossa (PF) only versus PF + pelvis (P)] before knowledge of the RIS findings were charted. The RIS findings, with regard to uptake in the PF, uptake in the P, or extrapelvic (EP) uptake were tabulated. Then, the RT treatment decisions based on the RIS knowledge were evaluated and compared with the pre-RIS RT treatment decisions.

RESULTS

Of the 54 patients originally referred for post-RRP RT, the initial decision was to recommend RT to the PF only in 52 cases and to PF+P in 2 cases. The RIS findings were as follows: PF only, 43 patients; PF+P, 8 patients; PF+EP, 2 patients; PF+P+EP, 1 patient. After knowledge of these RIS results, the decision to offer RT was withdrawn in 4 of 54 patients (7.4%; P = 0.046). Furthermore, RIS changed the general treatment volume (PF only to PF+P) in 6 of 54 patients (11.1%; P = 0.015). In total, RIS altered the RT decision in 10 of 54 patients (18.5%; P = 0.0067). Three-year biochemical failure-free survival (with failure defined as 2 consecutive prostate-specific antigen [PSA] rises above 0.2 ng/mL after PSA nadir) was 78%; no patient, disease, or treatment factor reached statistical significance on univariate or multivariate analysis.

CONCLUSION

RIS was found to influence post-RRP RT decision making for the identification of patients not likely to benefit from RT and for guiding general target volume definition.

Impact of radioimmunoscintigraphy on definition of clinical target volume for radiotherapy after prostatectomy

The goal of this study was to evaluate the role of radioimmunoscintigraphy (RIS) directed against prostate-specific membrane antigen in modifying postprostatectomy prostate fossa clinical target volume (CTV) definition.

METHODS

The records of 25 postprostatectomy patients who received external-beam radiotherapy after prostatectomy and who underwent vessel-based RIS/planning CT registration were reviewed. For each patient, the CTV that would have been treated (CTV(pre)) before this registration was compared with that defined after the registration (CTV(post)). In addition, using a standard dose of 66 Gy in 2-Gy fractions, the corresponding bladder and rectum dose volume histograms were compared using 2 endpoints: volume receiving > or =60 Gy (V60) and area under the curve (AUC).

RESULTS

The mean CTV(pre) vs. CTV(post) volumes were 24.4 vs. 35.0 cm(3), respectively (P = 0.032). The V60 results for CTV(pre) and CTV(post) were 32.7 vs. 41.0 cm(3), respectively, for the rectum (P = 0.168) and 33.9 vs. 46.6 cm(3), respectively, for the bladder (P = 0.015). The AUC results for CTV(pre) and CTV(post) were 4,027 vs. 4,516 Gy x cm(3), respectively, for the rectum (P = 0.396) and 4,782 vs. 5,561, respectively, for the bladder (P = 0.119). No Radiation Therapy Oncology Group grade 3, 4, or 5 (acute or late, gastrointestinal, or genitourinary) toxicity was observed. Two-year biochemical failure-free survival (with failure defined as 2 consecutive prostate-specific antigen rises above 0.2ng/mL) was 87% for the cohort.

CONCLUSION

Incorporating RIS uptake resulted in significant modifications in CTV definition. The consequences of these modifications on the rectum V60 or AUC or on the bladder AUC were not significant, although the bladder V60 did increase. However, observed toxicity was low, with acceptable short-term biochemical control, suggesting that treatment to the modified CTV was tolerable.

Impact of hormone therapy when combined with external beam radiotherapy for early-stage, intermediate-, or high-risk prostate cancer

The purpose of this investigation was to explore the potential benefit of hormone therapy in addition to external beam radiotherapy for patients with early-stage (T1-2), intermediate-(prostate-specific antigen [PSA] > 10 or Gleason score >or= 7) or high-risk (PSA > 10 and Gleason score >or= 7) prostate cancer. The charts of 412 patients with early-stage intermediate- and high-risk prostate cancer treated with external beam radiotherapy with or without a 4-month total androgen blockade were reviewed. The groups were balanced with respect to age, pretreatment PSA, and stage, but differed with respect to Gleason score and radiation dose. Biochemical failure rates, as defined by the ASTRO consensus panel, were compared between those receiving and those not receiving hormones. With a median follow-up of 2.0 years, the biochemical failure rate was 12.1 versus 23.1% (p = 0.02) in favor of those receiving hormones. This difference was seen for the subgroups followed for more than 6 months (12.5 vs. 25.0%), more than 9 months (14.5 vs. 26.3%), and more than 12 months (17.3 vs. 27.0%). Thus, biochemical failure decreased with the administration of hormone therapy in this group of patients with early stage, intermediate- or high-risk prostate cancer. This finding requires validation by ongoing randomized trials.

Biological-effective versus conventional dose volume histograms correlated with late genitourinary and gastrointestinal toxicity after external beam radiotherapy for prostate cancer: a matched pair analysis

BACKGROUND

To determine whether the dose-volume histograms (DVH's) for the rectum and bladder constructed using biological-effective dose (BED-DVH's) better correlate with late gastrointestinal (GI) and genitourinary (GU) toxicity after treatment with external beam radiotherapy for prostate cancer than conventional DVH's (C-DVH's).

METHODS

The charts of 190 patients treated with external beam radiotherapy with a minimum follow-up of 2 years were reviewed. Six patients (3.2%) were found to have RTOG grade 3 GI toxicity, and similarly 6 patients (3.2%) were found to have RTOG grade 3 GU toxicity. Average late C-DVH's and BED-DVH's of the bladder and rectum were computed for these patients as well as for matched-pair control patients. For each matched pair the following measures of normalized difference in the DVH's were computed: (a) deltaAUC = (Area Under Curve [AUC] in grade 3 patient--AUC in grade 0 patient)/(AUC in grade 0 patient) and (b) deltaV60 = (Percent volume receiving = 60 Gy [V60] in grade 3 patient--V60 in grade 0 patient)/(V60 in grade 0 patient).

RESULTS

As expected, the grade 3 curve is to the right of and above the grade 0 curve for all four sets of average DVH's--suggesting that both the C-DVH and the BED-DVH can be used for predicting late toxicity. deltaAUC was higher for the BED-DVH's than for the C-DVH's--0.27 vs 0.23 (p = 0.036) for the rectum and 0.24 vs 0.20 (p = 0.065) for the bladder. deltaV60 was also higher for the BED-DVH's than for the C-DVH's--2.73 vs 1.49 for the rectum (p = 0.021) and 1.64 vs 0.71 (p = 0.021) for the bladder.

CONCLUSIONS

When considering well-established dosimetric endpoints used in evaluating treatment plans, BED-DVH's for the rectum and bladder correlate better with late toxicity than C-DVH's and should be considered when attempting to minimize late GI and GU toxicity after external beam radiotherapy for prostate cancer.