Overall survival in Japanese patients with ER+/HER2- advanced breast cancer treated with first-line palbociclib plus letrozole.

BACKGROUND: An open-label, single-arm, Japanese phase 2 study (J-Ph2) investigated the efficacy and safety of first-line (1L) palbociclib (PAL) + letrozole (LET) in postmenopausal Japanese women with ER+/HER2- advanced breast cancer (ABC). In the final analysis, median progression-free survival was 35.7 months (95% CI 21.7-46.7); but overall survival (OS) data were immature. Here, we report the findings from a follow-up study of J-Ph2 (NCT04735367) evaluating OS and subsequent therapy in these Japanese women. METHODS: Patients (N = 42) who participated in J-Ph2 were enrolled in the OS follow-up study. The primary endpoint was OS and secondary endpoints included type and duration of subsequent therapy. RESULTS: Patients were a median age of 62.5 years; 48% had visceral metastases. At a median follow-up of 89.7 months, the median OS was 85.4 months (95% CI 64.3-not estimable). Median OS was longer in patients with nonvisceral versus visceral metastases (not reached vs 67.3 months), or with treatment-free interval > 12 months versus ≤ 12 months (85.4 vs 45.4 months), or with treatment duration ≥ 24 months versus < 24 months (not reached vs 47.5 months). Of patients who received a first subsequent therapy (81%), most (67%) continued endocrine-based therapy, while 7% received chemotherapy. The median duration of the first subsequent therapy was 8.3 months (95% CI 3.9-12.2), and the median chemotherapy-free survival was 69.1 months (95% CI 24.2-85.4). CONCLUSIONS: In this population of Japanese women with ER+/HER2- ABC, median OS was over 7 years with 1L PAL + LET, supporting the use of 1L PAL + endocrine therapy. TRIAL NUMBER: NCT04735367.

Real-world treatment patterns of subsequent therapy after palbociclib in patients with advanced breast cancer in Japan.

PURPOSE: The optimal treatment following endocrine therapy (ET) plus a cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) has not been established. We aimed to investigate treatment patterns and time to treatment failure (TTF) of subsequent therapy after palbociclib in a Japanese real-world setting. METHDS: This retrospective observational study used de-identified data of patients with advanced breast cancer treated with palbociclib, using a nationwide claims database (April 2008 to June 2021). Measures included the type of subsequent therapies after palbociclib (endocrine-based therapy: ET alone, ET + CDK4/6i, and ET + mammalian target of rapamycin inhibitor [mTORi]; chemotherapy; chemotherapy + ET; and others) and their TTFs. The median TTF and 95% confidence interval (CI) were estimated using the Kaplan-Meier method. RESULTS: Of 1170 patients treated with palbociclib, 224 and 235 received subsequent therapies after first- and second-line palbociclib treatment, respectively. Among them, 60.7% and 52.8% were treated with endocrine-based therapies as first subsequent therapy, including ET + CDK4/6i (31.2% and 29.8%, respectively). The median TTF (95% CI) of ET alone, ET + CDK4/6i, and ET + mTORi as first subsequent therapy after first-line palbociclib were 4.4 (2.8-13.7), 10.9 (6.5-15.6), and 6.1 (5.1-7.2) months, respectively. No apparent relationship between the treatment duration of prior ET + palbociclib and subsequent abemaciclib was observed. CONCLUSION: This real-world study revealed that one-third of the patients received sequential CDK4/6i after ET + palbociclib, and treatment duration of ET + CDK4/6i following ET + palbociclib was the longest among the treatment options. Further data are awaited to determine whether ET + targeted therapy with CDK4/6i and mTORi provides acceptable treatment options following ET + palbociclib.

Real-world treatment patterns of palbociclib and blood count monitoring in patients with advanced breast cancer in Japan.

Aim: To reveal the treatment patterns of palbociclib and complete blood count (CBC) monitoring in a Japanese real-world setting. Materials & methods: Deidentified data of patients with advanced breast cancer who received palbociclib from 2017 to 2020 were examined from a Japanese claims database. Results & conclusion: We identified 1074 patients. Palbociclib was commonly prescribed as second- or later-line treatment in 2017/2018; thereafter its first-line treatment increased. Regardless of treatment lines, fulvestrant was most commonly prescribed in combination with palbociclib (57-66% in the first-third-line), and this finding differed from that in the USA. Most patients initiated palbociclib at 125 mg/day; however, over a half of patients reduced doses within the first 8 weeks. Although CBC was regularly monitored, some patients did not undergo blood tests. Early dose reduction and CBC monitoring should be performed cautiously to minimize safety concern and prevent early treatment discontinuation.

Analysis of subsequent therapy in Japanese patients with hormone receptor‒positive/human epidermal growth factor receptor 2‒negative advanced breast cancer who received palbociclib plus endocrine therapy in PALOMA-2 and -3.

BACKGROUND: In the double-blind, phase 3 PALOMA-2 and PALOMA-3 studies, palbociclib plus endocrine therapy (ET) demonstrated significant improvement in progression-free survival versus placebo plus ET in patients with hormone receptor‒positive/human epidermal growth factor receptor 2‒negative advanced breast cancer. This analysis assessed subsequent treatment patterns after palbociclib therapy in Japanese patients enrolled in the PALOMA-2 and PALOMA-3 studies. METHODS: PALOMA-2 included postmenopausal women who had not received prior systemic therapy for advanced disease. PALOMA-3 included pre- or postmenopausal women who had progressed on previous ET. Types of subsequent therapy were assessed, and treatment durations of subsequent therapy were estimated using the Kaplan-Meier method. RESULTS: Japanese patients were enrolled in PALOMA-2 (n = 46) and PALOMA-3 (n = 35). In both studies, the most common first subsequent therapy was ET (PALOMA-2, 77% in the palbociclib group and 75% in the placebo group; PALOMA-3, 55% and 43%, respectively), followed by chemotherapy (PALOMA-2, 18% and 8%; PALOMA-3, 32% and 57%). The median (95% CI) duration of first subsequent therapy was 6.4 (2.3‒13.9) months with palbociclib plus letrozole and 6.7 (2.8‒13.0) months with placebo plus letrozole in PALOMA-2 and 3.8 (2.4‒5.7) months with palbociclib plus fulvestrant and 9.7 (1.0‒not estimable) months with placebo plus fulvestrant in PALOMA-3. CONCLUSIONS: The types of first subsequent therapy received by Japanese patients in the palbociclib plus ET and placebo plus ET groups were similar. Further evaluation of subsequent therapy data in the real-world setting is warranted considering the small sample size of this analysis.

Palbociclib-letrozole as first-line treatment for advanced breast cancer: Updated results from a Japanese phase 2 study.

Palbociclib is a highly selective, reversible, oral inhibitor of cyclin-dependent kinases 4 and 6 that is approved to treat hormone receptor-positive/human epidermal growth factor receptor 2-negative advanced breast cancer. An open-label, single-arm, Japanese phase 2 study was conducted to investigate the efficacy and safety of palbociclib plus letrozole as first-line treatment in 42 postmenopausal patients with estrogen receptor-positive/human epidermal growth factor receptor 2-negative advanced breast cancer. The probability of progression-free survival originally reported at 1 year was 75.0% (90% confidence interval, 61.3-84.4), but median progression-free survival was not attained at the primary analysis. In this report, updated efficacy and safety results with a longer follow-up period are presented. The median duration of treatment in the updated analysis was 33.0 months (range, 1.8-49.2). The probability of progression-free survival at 1 year was 75.6% (90% confidence interval, 62.4-84.7). Median progression-free survival was 35.7 months (95% confidence interval, 21.7-46.7). Objective response rate and disease control rate were 47.6% (95% confidence interval, 32.0-63.6) and 85.7% (95% confidence interval, 71.5-94.6), respectively. Common treatment-related adverse events (all grades; grade 3/4) were neutropenia (100%; 93%), leukopenia (83%; 60%), and stomatitis (76%; 0%). Treatment-related febrile neutropenia was reported in one patient. In general, no clinically meaningful deterioration in health-related quality of life was observed. Palbociclib plus letrozole remained effective and tolerable in Japanese postmenopausal patients with estrogen receptor-positive, human epidermal growth factor receptor 2-negative advanced breast cancer in this updated analysis.

Correction to: Neutropenia management with palbociclib in Japanese patients with advanced breast cancer.

The correct name of the last author should be "Masakazu Toi", and not ''Masakuzu Toi" as given in the original publication of the article.

Neutropenia management with palbociclib in Japanese patients with advanced breast cancer.

BACKGROUND: The cyclin-dependent kinase 4/6 (CDK4/6) inhibitor palbociclib, in combination with endocrine therapy (ET), significantly prolonged progression-free survival in women with hormone receptor-positive, human epidermal growth factor receptor 2-negative advanced breast cancer (HR+/HER2- ABC) in PALOMA-2 and PALOMA-3. Neutropenia and palbociclib dose reductions/interruptions occurred more frequently in the Japanese versus overall populations. We evaluated neutropenia patterns, palbociclib dose management, and clinical responses after dose reduction in Japanese patients in PALOMA-2 and PALOMA-3 and a single-arm Japanese phase 2 study. METHODS: PALOMA-2 and the Japanese phase 2 study enrolled postmenopausal women with estrogen receptor-positive, HER2- ABC who had not received prior systemic therapy for advanced disease; PALOMA-3 enrolled women with HR+/HER2- ABC, regardless of menopausal status, whose disease had progressed after prior ET. Palbociclib (125 mg/day) was administered 3 weeks on/1 week off. Dose reduction/interruption, cycle delay, tumor response, and laboratory-assessed neutropenia were analyzed in Japanese patients who received palbociclib. RESULTS: A total of 101 Japanese patients received palbociclib + ET. Among Japanese patients in the 3 studies, the frequency of all-grade/grade 3/grade 4 neutropenia was 94%/53%/34%, 100%/69%/21%, and 100%/67%/26%, respectively. Twenty (63%), 28 (67%), and 15 (56%) patients required palbociclib dose reduction. Dose interruption or reduction did not affect palbociclib treatment duration, and durable tumor response was observed despite dose reduction. CONCLUSION: Neutropenia was manageable with dose modifications, without affecting palbociclib treatment duration or efficacy. TRIAL REGISTRATION: Pfizer (NCT01740427, NCT01684215, NCT01942135).

Palbociclib in combination with fulvestrant in patients with hormone receptor-positive, human epidermal growth factor receptor 2-negative advanced breast cancer: PALOMA-3 subgroup analysis of Japanese patients.

BACKGROUND: In the double-blind, phase 3 PALOMA-3 study, palbociclib-fulvestrant significantly prolonged progression-free survival versus placebo-fulvestrant in patients with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) metastatic breast cancer (MBC) whose disease had progressed on prior endocrine therapy. The present study evaluated the efficacy, safety, and pharmacokinetics of palbociclib plus fulvestrant in Japanese patients enrolled in PALOMA-3. METHODS: Pre/peri/postmenopausal women with HR+/HER2- MBC were randomized 2:1 to fulvestrant (500 mg) and either palbociclib (125 mg/day; 3 weeks on/1 week off; n = 347) or placebo (n = 174). Prespecified exploratory analyses compared the efficacy (data cutoff: October 23, 2015), safety, and pharmacokinetics (data cutoff: December 5, 2014) in Japanese women versus the overall population. RESULTS: A total of 35 Japanese women were randomized to palbociclib-fulvestrant (n = 27) or placebo-fulvestrant (n = 8). Median progression-free survival was 13.6 months (95% CI, 7.5-not estimable) in the Japanese palbociclib-fulvestrant group and 11.2 months (95% CI, 5.6-not estimable) in the placebo-fulvestrant group. The most common adverse event (AE) in Japanese patients was neutropenia (all grades, 93%); no discontinuations were due to an AE. Geometric mean trough concentration values (within-subject mean steady state) for palbociclib were similar for Japanese Asian (excluding Japanese), and non-Asian patients (84.4 ng/mL, 86.3 ng/mL, and 74.8 ng/mL, respectively). CONCLUSION(S): The results for the overall population and Japanese patients in PALOMA-3 suggest that palbociclib plus fulvestrant was effective and well tolerated in Japanese patients with HR+/HER2‒ MBC whose disease had progressed on prior endocrine therapy (Pfizer; NCT01942135).

Palbociclib in combination with letrozole in patients with estrogen receptor-positive, human epidermal growth factor receptor 2-negative advanced breast cancer: PALOMA-2 subgroup analysis of Japanese patients.

BACKGROUND: In PALOMA-2, palbociclib-letrozole significantly improved progression-free survival (PFS) vs placebo-letrozole in women with estrogen receptor-positive, human epidermal growth factor receptor 2-negative (ER+/HER2-) advanced breast cancer (ABC) in the first-line setting. We evaluated the efficacy, safety, and pharmacokinetics of palbociclib in Japanese women in PALOMA-2. METHODS: In this phase 3 study, 666 postmenopausal women with ER+/HER2- ABC were randomized 2:1 to palbociclib (125 mg/day [3 weeks on/1 week off]) plus letrozole (2.5 mg daily) or placebo plus letrozole. A prespecified, exploratory, subgroup analysis of Japanese patients (n = 46) was conducted to compare results with those of the overall population. RESULTS: At the February 26, 2016 cutoff, median PFS among the 46 Japanese patients was 22.2 months (95%CI, 13.6‒not estimable) with palbociclib-letrozole vs 13.8 months (5.6‒22.2) with placebo-letrozole (hazard ratio, 0.59 [95%CI, 0.26-1.34]). The most common adverse events (AEs) were hematologic and more frequent among Japanese patients than the overall population (neutropenia: 93.8% [87.5% grade 3/4] vs 79.5% [66.4%]; leukopenia: 62.5% [43.8%] vs 39.0% [24.8%]); no Japanese patients had febrile neutropenia. Palbociclib dose reductions due to toxicity (mainly neutropenia) were more common in Japanese patients (62.5% vs 36.0%); few permanently discontinued due to AEs. Although mean palbociclib trough concentration was higher in Japanese patients vs non-Asians (95.4 vs 61.7 ng/mL), the range of individual values of the Japanese patients was within that of non-Asians. CONCLUSIONS: These results from PALOMA-2 suggest that palbociclib-letrozole merits consideration as a first-line treatment option for postmenopausal Japanese patients with ER+/HER2‒ ABC. ClinicalTrials.gov: NCT01740427.

Palbociclib in combination with letrozole as first-line treatment for advanced breast cancer: A Japanese phase II study.

This single-arm, open-label, phase II study in 42 Japanese postmenopausal patients with estrogen receptor-positive/human epidermal growth factor receptor 2-negative (ER+/HER2-) advanced breast cancer evaluated the efficacy, safety, and pharmacokinetics of first-line palbociclib (125 mg once daily, 3 weeks on/1 week off) coadministered with letrozole (2.5 mg once daily). Primary endpoint of investigator-assessed 1-year progression-free survival (PFS) probability was 75.0% (90% CI, 61.3%-84.4%), far surpassing the 40% lower limit of the 90% CI supporting efficacy. Median duration of treatment was 438 days. Among secondary efficacy measures, median PFS was not reached (95% CI, 16.7: not estimable), 17/42 patients (40.5%) had an objective response, 36/42 (85.7%) maintained disease control, and 27/42 (64.3%) remained in follow-up. Median overall survival was not reached, and 1-year survival probability was 92.9% (95% CI, 79.5%-97.6%). Results of intensive pharmacokinetics in a subset of 6 patients showed palbociclib steady-state mean area under the plasma concentration-time curve over the dosing interval [τ] and mean maximum plasma concentration were 1979 ng·h/mL and 124.7 ng/mL, respectively. For day 15 plasma samples from cycles 1 and 2, geometric mean of the within-patient mean trough concentration was 90.1 ng/mL. The most common treatment-related adverse events were neutropenia (100%) and stomatitis (73.8%). There was 1 case of treatment-related febrile neutropenia. Toxicities were generally tolerated and manageable by dose modifications and/or medical care. Efficacy and safety of first-line palbociclib plus letrozole therapy is supported in Japanese postmenopausal patients with treatment-naive ER+/HER2- advanced breast cancer.

A design strategy for small molecule-based targeted MRI contrast agents: their application for detection of atherosclerotic plaques.

Gadolinium(III) ion (Gd(3+)) complexes are widely used as contrast agents in magnetic resonance imaging (MRI), and many attempts have been made to couple them to sensor moieties in order to visualize biological phenomena of interest inside the body. However, the low sensitivity of MRI has made it difficult to develop practical MRI contrast agents for in vivo imaging. We hypothesized that practical MRI contrast agents could be designed by targeting a specific biological environment, rather than a specific protein such as a receptor. To test this idea, we designed and synthesized a Gd(3+)-based MRI contrast agent, 2BDP3Gd, for visualizing atherosclerotic plaques by linking the Gd(3+)-complex to the lipophilic fluorophore BODIPY to stain lipid-rich environments. We found that 2BDP3Gd was selectively accumulated into lipid droplets of adipocytes at the cellular level. Atherosclerotic plaques in the aorta of Watanabe heritable hyperlipidemic (WHHL) rabbits were clearly visualized in T1-weighted MR images after intravenous injection of 2BDP3Gd in vivo.

Method for enhancing cell penetration of Gd3+-based MRI contrast agents by conjugation with hydrophobic fluorescent dyes.

Gadolinium ion (Gd(3+)) complexes are commonly used as magnetic resonance imaging (MRI) contrast agents to enhance signals in T(1)-weighted MR images. Recently, several methods to achieve cell-permeation of Gd(3+) complexes have been reported, but more general and efficient methodology is needed. In this report, we describe a novel method to achieve cell permeation of Gd(3+) complexes by using hydrophobic fluorescent dyes as a cell-permeability-enhancing unit. We synthesized Gd(3+) complexes conjugated with boron dipyrromethene (BDP-Gd) and Cy7 dye (Cy7-Gd), and showed that these conjugates can be introduced efficiently into cells. To examine the relationship between cell permeability and dye structure, we further synthesized a series of Cy7-Gd derivatives. On the basis of MR imaging, flow cytometry, and ICP-MS analysis of cells loaded with Cy7-Gd derivatives, highly hydrophobic and nonanionic dyes were effective for enhancing cell permeation of Gd(3+) complexes. Furthermore, the behavior of these Cy7-Gd derivatives was examined in mice. Thus, conjugation of hydrophobic fluorescent dyes appears to be an effective approach to improve the cell permeability of Gd(3+) complexes, and should be applicable for further development of Gd(3+)-based MRI contrast agents.

Design and synthesis of a highly sensitive off-on fluorescent chemosensor for zinc ions utilizing internal charge transfer.

Fluorescence imaging is a powerful tool for the visualization of biological molecules in living cells, tissue slices, and whole bodies, and is important for elucidating biological phenomena. Furthermore, zinc (Zn(2+)) is the second most abundant heavy metal ion in the human body after iron, and detection of chelatable Zn(2+) in biological studies has attracted much attention. Herein, we present a novel, highly sensitive off-on fluorescent chemosensor for Zn(2+) by using the internal charge transfer (ICT) mechanism. The rationale of our approach to highly sensitive sensor molecules is as follows. If fluorescence can be completely quenched in the absence of Zn(2+), chemosensors would offer a better signal-to-noise ratio. However, it is difficult to quench the fluorescence completely before Zn(2+) binding, and most sensor molecules still show very weak fluorescence in the absence of Zn(2+). But even though the sensor shows a weak fluorescence in the absence of Zn(2+), this fluorescence can be further suppressed by selecting an excitation wavelength that is barely absorbed by the Zn(2+)-free sensor molecule. Focusing on careful control of ICT within the 4-amino-1,8-naphthalimide dye platform, we designed and synthesized a new chemosensor (1) that shows a pronounced fluorescence enhancement with a blueshift in the absorption spectrum upon addition of Zn(2+). The usefulness of 1 for monitoring Zn(2+) changes was confirmed in living HeLa cells. There have been several reports on 4-amino-1,8-naphthalimide-based fluorescent sensor molecules. However, 1 is the first Zn(2+)-sensitive off-on fluorescent sensor molecule that employs the ICT mechanism; most off-on sensor molecules for Zn(2+) employ the photoinduced electron transfer (PeT) mechanism.