A phase Ib/II study of eribulin in combination with cyclophosphamide in patients with advanced breast cancer

PURPOSE

We hypothesized that eribulin combined with cyclophosphamide (EC) would be an effective combination with tolerable toxicity for the treatment of advanced breast cancer (ABC).

METHODS

Patients with histologically confirmed metastatic or unresectable ABC with any number of prior lines of therapy were eligible to enroll. In the dose escalation cohort, dose level 0 was defined as eribulin 1.1 mg/m2 and cyclophosphamide 600 mg/m2, and dose level 1 was defined as eribulin 1.4 mg/m2 and cyclophosphamide 600 mg/m2. Eribulin was given on days 1 and 8 and cyclophosphamide on day 1 of a 21-day cycle. In the dose expansion cohort, enrollment was expanded at dose level 1. The primary objective was clinical benefit rate (CBR), and secondary objectives were response rate (RR), duration of response (DOR), progression-free survival (PFS), and safety.

RESULTS

No dose-limiting toxicities were identified in the dose escalation cohort (n = 6). In the dose expansion cohort, an additional 38 patients were enrolled for a total of 44 patients, including 31 patients (70.4%) with hormone receptor-positive (HR +)/HER2- disease, 12 patients (27.3%) with triple-negative breast cancer (TNBC), and 1 patient (2.3%) with HR + /HER2 + disease. Patients had a median age of 56 years (range 33-82 years), 1 prior line of hormone therapy (range 0-6), and 2 prior lines of chemotherapy (range 0-7). CBR was 79.5% (35/44; 7 partial response, 28 stable disease) and the median DOR was 16.4 weeks (range 13.8-21.1 weeks). Median PFS was 16.4 weeks (95% CI: 13.8-21.1 weeks). The most common grade 3/4 adverse event was neutropenia (47.7%, n = 21). Fourteen of 26 patients (53.8%) with circulating tumor cell (CTC) data were CTC-positive ([Formula: see text] 5 CTC/7.5 mL) at baseline. Median PFS was shorter in patients who were CTC-positive vs. negative (13.1 vs 30.6 weeks, p = 0.011).

CONCLUSION

In heavily pretreated patients with ABC, treatment with EC resulted in an encouraging CBR of 79.5% and PFS of 16.4 weeks, which compares favorably to single-agent eribulin. Dose reduction and delays were primarily due to neutropenia. The contribution of cyclophosphamide to eribulin remains unclear but warrants further evaluation. NCT01554371.

Abstract PS2-19: Circulating tumor cell (CTC) enumeration in a phase II trial of pazopanib in addition to endocrine therapy in patients with hormone resistant advanced breast cancer (ABC)

Background: CTCs are detectable in approximately 50% of pts with metastatic breast cancer, and elevated CTC levels are an independent negative prognostic factor. CTCs have been shown to play a valuable role in predicting outcomes in pts with ABC treated with chemotherapy or endocrine therapy. This phase II trial was conducted to evaluate the clinical benefit (CB) of pazopanib, a VEGF receptor tyrosine kinase inhibitor (TKI) combined with nonsteroidal aromatase inhibitors (NSAIs) in pts with ABC resistant to NSAIs. As an exploratory analysis, we hypothesized that CTC levels might be correlated with response to pazopanib plus endocrine therapy.

Methods: Eligibility included postmenopausal women with hormone receptor positive (HR+) ABC and progressive disease after at least one month of NSAIs. Treatment was pazopanib 800 mg/day plus either letrozole or anastrozole. The primary endpoint was clinical benefit rate at 12 weeks (CBR12, wks). Secondary endpoints included progression free survival (PFS), safety, and the impact of pazopanib and NSAI on CTCs. A CBR of 20% was considered a clinically meaningful comparison to the expected CBR of <5% with continued NSAIs after PD. Blood samples were collected for CTC analysis at baseline, then every 4 wks while on treatment. The presence of CTCs was assessed using the FDA-cleared CellSearch System; CTCs were defined as EPCAM-positive, CD45-negative nucleated cells. Samples with 5 CTCs per 7.5 mLs of blood were considered CTC-positive.

Results: 32 pts were enrolled; 28 are evaluable for study endpoints. The median age was 58 years (range: 41-77). Pts were heavily pre-treated, with a median of 2 prior hormone therapies (range 1-6) and 1 prior chemotherapy (range 0-8). 8 pts (28.6%) stopped treatment due to adverse events, and 6 pts progressed before wk 12. CBR12 was 46.4% (12 SD, 1 PR), and CBR24 was 25% (5 SD, 2 PR). Safety has been presented (ASCO 2020). Median PFS was 20 wks, and median PFS for pts with CBR12 was 24 wks. Five (22%) of 23 pts with CTC data were CTC-positive (5 CTC/7.5 mL). There was no significant association between CBR12 and CTC status at baseline, or between CBR12 and change in CTC status (baseline to 4 wks after initiation of treatment). 7 pts had non-CBR12 and CTC data; 4 pts (n=4/7; 57%) were CTC positive at either baseline, week 4 or both. 11 pts had CBR12 and CTC data; all patients were CTC negative at baseline and remained negative at 4 wks. 7 pts had PFS >6 months (24, 32, 36, 36, 48, 184 and 274 wks), and 6 had CTC data: all were CTC-negative at baseline and 4 wks, then remained negative at 12 wks. Based on baseline values only, CTC-positive pts had a shorter median PFS compared to CTC-negative pts, but the difference was not statistically significant (11 wks vs 14 wks, p=0.18). Persistently CTC negative patients had significantly longer PFS compared to patients who were CTC positive at any time during study treatment (36 wks vs 11 wks, p=0.01).

Conclusions: The addition of pazopanib to NSAIs resulted in a CBR12 of 46.4%, and a CBR24 of 25% in pts with heavily pre-treated ABC resistant to NSAIs. These results support clinical efficacy of antiangiogenic TKI in HR+ ABC and suggest benefit in hormone resistant disease. Consistently negative CTCs correlated with response and response duration. PFS was significantly longer in patients who were consistently CTC negative, further defining the prognostic role of CTCs in HR+ ABC. (NCT01466972)

Citation Format: Ozge Gumusay, Mark Jesus M. Magbanua, Melanie C. Majure, Travis Deal, Jonathan R. Renslo, Chiara A. Wabl, Michelle E. Melisko, A. Jo Chien, Andrei Goga, Mark M. Moasser, John W. Park, Jimmy Hwang, Hope S. Rugo. Circulating tumor cell (CTC) enumeration in a phase II trial of pazopanib in addition to endocrine therapy in patients with hormone resistant advanced breast cancer (ABC) [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS2-19.

Maintenance of tolerance by regulation of anti-myeloperoxidase B cells

Anti-neutrophil cytoplasmic autoantibodies directed toward myeloperoxidase or proteinase 3 are detected in sera of patients with small vessel vasculitis and participate in the pathogenesis of this disease. Autoantibodies develop when self-reactive B cells escape the regulation that ensures self-tolerance. In this study, regulation of anti-myeloperoxidase B cells was examined in mice that express an anti-myeloperoxidase Vkappa1C-Jkappa5 light-chain transgene, which confers anti-myeloperoxidase specificity when combined with a variety of heavy chains. Vkappa1C-Jkappa5 transgenic mice have splenic anti-myeloperoxidase B cells but do not produce circulating anti-myeloperoxidase antibodies. Two groups of transgenic mice that differed by their relative dosage of the transgene were compared; high-copy mice had a mean relative transgene dosage of 1.92 compared with 1.02 in the low-copy mice. These mice exhibited a 90 and 60% decrease in mature follicular B cells, respectively. High-copy mice were characterized by a large population of anti-myeloperoxidase B cells, a preponderance of B-1 cells, and an increased percentage of apoptotic myeloperoxidase-binding B cells. Low-copy mice had similar changes in B cell phenotype with the exception of an expanded marginal zone population. B cells from low-copy mice but not high-copy mice produced anti-myeloperoxidase antibodies after stimulation with lipopolysaccharide. These results indicate that tolerance to myeloperoxidase is maintained by central and peripheral deletion and that some myeloperoxidase-binding B cells are positively selected into the marginal zone and B-1 B cell subsets. A defect in these regulatory pathways could result in autoimmune disease.

Inhalation of Francisella novicida Delta mglA causes replicative infection that elicits innate and adaptive responses but is not protective against invasive pneumonic tularemia

Francisella tularensis causes the zoonosis tularemia in humans, and inhaled F. tularensis ssp. novicida induces lethal murine tularemia. Transcription of virulence factors in F. novicida is regulated by macrophage growth locus A (mglA), a global regulator required for bacterial replication in macrophages in vitro. We examined the infectivity and immunogenicity of attenuated F. novicida Delta mglA in the lung in vivo. Aerosolized Delta mglA caused replicative pulmonary infection that peaked at 7 days and was cleared thereafter, without clinical evidence of disease. In contrast, inhalation of wild type F. novicida resulted in more rapid bacterial replication and dissemination leading to death within 96 h. Early containment of Delta mglA infection was partially dependent on myeloid differentiation factor 88 and interferon-gamma but did not require B or T cells. However, lymphocytes were necessary for subsequent bacterial clearance. Infection with Delta mglA elicited specific IgG1-predominant antibodies and variable interferon-gamma recall responses to wild type F. novicida. Inoculation of mice with aerosolized Delta mglA afforded no protection against a subsequent low-dose aerosol challenge with wild type F. novicida. These findings establish that inhalation of F. novicida Delta mglA results in replicative infection that elicits innate and adaptive immune responses but not protective immunity against invasive pneumonic tularemia.