Tuning the Metabolic Stability of Visual Cycle Modulators through Modification of an RPE65 Recognition Motif

In the eye, the isomerization of all-trans-retinal to 11-cis-retinal is accomplished by a metabolic pathway termed the visual cycle that is critical for vision. RPE65 is the essential trans-cis isomerase of this pathway. Emixustat, a retinoid-mimetic RPE65 inhibitor, was developed as a therapeutic visual cycle modulator and used for the treatment of retinopathies. However, pharmacokinetic liabilities limit its further development including: (1) metabolic deamination of the γ-amino-α-aryl alcohol, which mediates targeted RPE65 inhibition, and (2) unwanted long-lasting RPE65 inhibition. We sought to address these issues by more broadly defining the structure-activity relationships of the RPE65 recognition motif via the synthesis of a family of novel derivatives, which were tested in vitro and in vivo for RPE65 inhibition. We identified a potent secondary amine derivative with resistance to deamination and preserved RPE65 inhibitory activity. Our data provide insights into activity-preserving modifications of the emixustat molecule that can be employed to tune its pharmacological properties.

Rational Alteration of Pharmacokinetics of Chiral Fluorinated and Deuterated Derivatives of Emixustat for Retinal Therapy

Recycling of all-trans-retinal to 11-cis-retinal through the visual cycle is a fundamental metabolic pathway in the eye. A potent retinoid isomerase (RPE65) inhibitor, (R)-emixustat, has been developed and tested in several clinical trials; however, it has not received regulatory approval for use in any specific retinopathy. Rapid clearance of this drug presents challenges to maintaining concentrations in eyes within a therapeutic window. To address this pharmacokinetic inadequacy, we rationally designed and synthesized a series of emixustat derivatives with strategically placed fluorine and deuterium atoms to slow down the key metabolic transformations known for emixustat. Crystal structures and quantum chemical analysis of RPE65 in complex with the most potent emixustat derivatives revealed the structural and electronic bases for how fluoro substituents can be favorably accommodated within the active site pocket of RPE65. We found a close (∼3.0 Å) F-π interaction that is predicted to contribute ∼2.4 kcal/mol to the overall binding energy.

Two different first-line 5-fluorouracil regimens with or without oxaliplatin in patients with metastatic colorectal cancer

BACKGROUND

Oxaliplatin, 5-fluorouracil (5-FU), and leucovorin (LV) are standard first-line treatments for patients with metastatic colorectal cancer (mCRC). The aim of this multicentre, open-label, phase IIIb study was to assess the addition of oxaliplatin to two different 5-FU regimens.

PATIENTS AND METHODS

Patients with previously untreated mCRC were randomised to arm A [two-weekly oxaliplatin 85 mg/m(2) + either continuous intravenous infusion (CIV) of 5-FU without LV or two-weekly bolus and CIV 5-FU + LV (LV5FU2)] or arm B (5-FU CIV or LV5FU2 alone). Irinotecan monotherapy was planned on progression.

RESULTS

A total of 725 patients were enrolled. After a fixed follow-up of 2 years for each patient, 2-year survival rates were 27.3% and 24.8% in arms A and B, respectively (hazard ratio 0.93; 95% confidence interval 0.78-1.10). The addition of oxaliplatin significantly improved response rates (54.1 versus 29.8%; P < 0.0001) and median progression-free survival (7.9 versus 5.9 months; P < 0.0001). The most common grade 3-4 toxic effects were neutropenia (arm A, 33%; arm B, 5%), diarrhoea (arm A, 14%; arm B, 8%), and fatigue (arm A, 9%; arm B, 8%).

CONCLUSIONS

Despite improved rates of tumour control, these results failed to demonstrate a survival benefit from the addition of oxaliplatin to infused 5-FU and lend further support to the use of sequential monotherapy in some patients with mCRC.

Randomized phase III study comparing irinotecan combined with 5-fluorouracil and folinic acid to cisplatin combined with 5-fluorouracil in chemotherapy naive patients with advanced adenocarcinoma of the stomach or esophagogastric junction

BACKGROUND

We aimed to establish the superiority (or noninferiority if superiority was not achieved) in terms of time to progression (TTP) of irinotecan/5-fluorouracil (IF) over cisplatin/5-fluorouracil (CF) in chemonaive patients with adenocarcinoma of the stomach/esophagogastric junction.

PATIENTS AND METHODS

Patients received either IF: i.v. irinotecan 80 mg/m(2) 30 min, folinic acid 500 mg/m(2) 2 h, 5-fluorouracil (5-FU) 2000 mg/m(2) 22 h, for 6/7 weeks or CF: cisplatin 100 mg/m(2) 1-3 h, with 5-FU 1000 mg/m(2)/day 24 h, days 1-5, every 4 weeks.

RESULTS

In all, 333 patients were randomized and treated (IF 170, CF 163). Patient characteristics were balanced except more IF patients had Karnofsky performance status 100%. TTP for IF was 5.0 months [95% confidence interval (CI) 3.8-5.8] and 4.2 months (95% CI 3.7-5.5) for CF (P = 0.088). Overall survival (OS) was 9.0 versus 8.7 months, response rate 31.8% versus 25.8%, time to treatment failure (TTF) 4.0 versus 3.4 months for IF and CF, respectively. The difference in TTF was statistically significant (P = 0.018). IF was better in terms of toxic deaths (0.6% versus 3%), discontinuation for toxicity (10.0% versus 21.5%), severe neutropenia, thrombocytopenia and stomatitis, but not diarrhea.

CONCLUSION

IF did not yield a significant TTP or OS superiority over CF, and the results of noninferiority of IF were borderline. However, IF may provide a viable, platinum-free front-line treatment alternative for metastatic gastric cancer.

Cetuximab with irinotecan in first-line treatment of epidermal growth factor receptor (EGFR)-expressing metastatic colorectal cancer (mCRC): Preliminary safety results (CRYSTAL)

3555

Background: Cetuximab is an IgG1 monoclonal antibody targeting the EGFR with proven activity in previously treated mCRC patients (pts). The modified two-weekly de Gramont regimen of irinotecan with infusional 5-fluorouracil (5-FU)/folinic acid (FA) (FOLFIRI) is a standard for metastatic disease. This randomized trial investigates the effectiveness of cetuximab with this chemotherapy combination versus chemotherapy alone in (pts) with EGFR-expressing mCRC previously untreated for metastatic disease. Methods: This phase III trial compares cetuximab (400 mg/m2 week 1 then 250 mg/m2 weekly) added to FOLFIRI (irinotecan 180 mg/m2, FA 400 mg/m2, 5-FU bolus 400 mg/m2, 2400 mg/m2 infusional 5-FU) (group A) vs. FOLFIRI alone (group B) in pts with EGFR-detectable tumors. 1080 pts are planned to detect a difference of ≥ 2 months in PFS with 80% power. The Data Safety Monitoring Board (DSMB) has performed an independent preplanned safety evaluation of 401 treated pts. Results: Pts (M/F 252/149, median age 62 years [range, 19–84], ECOG performance status [PS]: PS0, 57.1%: PS1, 38.4%: PS2, 4.5%) received at least 3 treatment cycles to date. Of the 401 pts, 83 (20.7%) pts completed/discontinued the trial. There were 11 deaths (2.7%) within 30 days of the last study treatment: 5 related to disease, 3 to chemotherapy, and 3 other (2 unknown, 1 intercurrent illness). Most common adverse events of the pooled safety data were skin reactions, diarrhea and nausea. Conclusions: After review of all relevant safety information by the DSMB, the trial continues. Recruitment was completed with 1220 patients in December 2005.

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Toxicity and health-related quality of life in breast cancer patients receiving adjuvant docetaxel, doxorubicin, cyclophosphamide (TAC) or 5-fluorouracil, doxorubicin and cyclophosphamide (FAC): impact of adding primary prophylactic granulocyte-colony stimulating factor to the TAC regimen

BACKGROUND

The aim of the study was to analyse the toxicity and health related quality of life (HRQoL) of breast cancer patients treated with FAC (5-fluorouracil, doxorubicin, cyclophosphamide) and TAC (docetaxel, doxorubicin, cyclophosphamide) with and without primary prophylactic G-CSF (PPG).

PATIENTS AND METHODS

This was a phase III study to compare FAC and TAC as adjuvant treatment of high-risk node-negative breast cancer patients. After the entry of the first 237 patients, the protocol was amended to include PPG in the TAC arm due to the high incidence of febrile neutropenia. A total of 1047 evaluable patients from 49 centres in Spain, two in Poland and four in Germany were included in the trial. Side-effects and the scores of the EORTC QLQ-C30 and QLQ BR-23 questionnaires were compared in the three groups (FAC, TAC pre-amendment and TAC post-amendment).

RESULTS

The addition of PPG to TAC significantly reduced the incidence of neutropenic fever, grade 2-4 anaemia, asthenia, anorexia, nail disorders, stomatitis, myalgia and dysgeusia. Patient QoL decreased during chemotherapy, more with TAC than FAC, but returned to baseline values afterwards. The addition of PPG to TAC significantly reduced the percentage of patients with clinically relevant Global Health Status deterioration (10 or more points over baseline value) at the end of chemotherapy (64% versus 46%, P<0.03).

CONCLUSIONS

The addition of PPG significantly reduces the incidence of neutropenic fever associated with TAC chemotherapy as well as that of some TAC-induced haematological and extrahaematological side-effects. The HRQoL of patients treated with TAC is worse than that of those treated with FAC but improves with the addition of PPG, particularly in the final part of chemotherapy treatment.

Irinotecan in combination with 5-fluorouracil and folinic acid or with cisplatin in patients with advanced gastric or esophageal-gastric junction adenocarcinoma: results of a randomized phase II study

BACKGROUND

To identify the most effective of two combinations, irinotecan/5-fluorouracil (5-FU)/folinic acid (FA) and irinotecan/cisplatin, in the treatment of advanced gastric cancer, for investigation in a phase III trial.

PATIENTS AND METHODS

Patients were randomized to receive irinotecan [80 mg/m2 intravenously (i.v.)], FA (500 mg/m2 i.v.) and a 22-h infusion of 5-FU (2000 mg/m2 i.v.), weekly for 6 weeks with a 1-week rest, or irinotecan (200 mg/m2 i.v.) and cisplatin (60 mg/m2 i.v.), on day 1 for 3 weeks.

RESULTS

A total of 115 patients were eligible for analysis in the per-protocol population. The overall response rate in the irinotecan/5-FU/FA arm (n=59) was 42.4%, with a complete response rate of 5.1%. Corresponding figures for the irinotecan/cisplatin arm (n=56) were 32.1% and 1.8%, respectively. The median time to progression was 6.5 months (irinotecan/5-FU/FA) and 4.2 months (irinotecan/cisplatin) (P < 0.0001), with median survival times of 10.7 and 6.9 months, respectively (P=0.0018). The major toxicity was grade 3/4 neutropenia, which was more pronounced with irinotecan/cisplatin than with irinotecan/5-FU/FA (65.7% versus 27%). Diarrhea was the main grade 3/4 non-hematological toxicity with both irinotecan/5-FU/FA (27.0%) and irinotecan/cisplatin (18.1%).

CONCLUSIONS

Both combinations were active, with acceptable safety profiles. Irinotecan/5-FU/FA was selected as the most effective combination for investigation in a phase III trial in advanced gastric cancer.

Oral capecitabine as an alternative to i.v. 5-fluorouracil-based adjuvant therapy for colon cancer: safety results of a randomized, phase III trial

BACKGROUND

Oral capecitabine achieves a superior response rate with an improved safety profile compared with bolus 5-fluorouracil-leucovorin (5-FU/LV) as first-line treatment for patients with metastatic colorectal cancer. We report here the results of a large phase III trial investigating adjuvant oral capecitabine compared with 5-FU/LV (Mayo Clinic regimen) in Dukes' C colon cancer.

PATIENTS AND METHODS

Patients aged 18-75 years with resected Dukes' C colon carcinoma were randomized to receive 24 weeks of treatment with either oral capecitabine 1250 mg/m(2) twice daily, days 1-14 every 21 days (n = 993), or i.v. bolus 5-FU 425 mg/m(2) with i.v. leucovorin 20 mg/m(2) on days 1-5, repeated every 28 days (n = 974).

RESULTS

Patients receiving capecitabine experienced significantly (P <0.001) less diarrhea, stomatitis, nausea/vomiting, alopecia and neutropenia, but more hand-foot syndrome than those receiving 5-FU/LV. Fewer patients receiving capecitabine experienced grade 3 or 4 neutropenia, febrile neutropenia/sepsis and stomatitis (P <0.001), although more experienced grade 3 hand-foot syndrome than those treated with 5-FU/LV (P <0.001). Capecitabine demonstrates a similar, favorable safety profile in patients aged <65 years or > or = 65 years old.

CONCLUSIONS

Based on its improved safety profile, capecitabine has the potential to replace 5-FU/LV as standard adjuvant treatment for patients with colon cancer. Efficacy results are expected to be available in Keywords: Adjuvant treatment, capecitabine, chemotherapy, colorectal cancer

A phase II study of intravenous navelbine and doxorubicin combination in previously untreated advanced breast carcinoma

PURPOSE

The combination of vinorelbine and doxorubicin, two very active drugs in metastatic breast cancer, has demonstrated impressive results in terms of efficacy, at the price of cardiac toxicity (10% grades 2-4) due to the cumulative dose of doxorubicin delivered. This study was designed to divide the dose of doxorubicin into two administrations (day 1 and 8) in order to reduce the toxicity profile, while keeping the same level of efficacy.

PATIENTS AND METHODS

Thirty-eight chemotherapy-naïve metastatic breast cancer patients entered into the study and were treated with vinorelbine, 25 mg/m(2), and doxorubicin, 25 mg/m(2), both on days 1 and 8, every 3 weeks. Thirty-seven patients were evaluable for efficacy and 38 for tolerance; 71% of the patients presented with visceral metastases.

RESULTS

Patients received a median of seven cycles and 94.9% of the intended dose intensity of both drugs. Grade 3-4 neutropenia was reported in 10% of cycles. Alopecia was reported in 89.5% of the patients, and grade 2 nausea/vomiting in 9.3% of the cycles. Grade 1-2 cardiac toxicity was noted in 23.7% of the patients. The objective response rate of the patients was 78.4% (nearly 81% for patients with visceral metastases); the median duration of response was 11.6 months, the median survival 21.6 months, and the 1-year survival 75.2%.

CONCLUSION

This schedule of vinorelbine/doxorubicin represents an active and well-tolerated combination.