Immuno-priming durvalumab with bevacizumab in HER2-negative advanced breast cancer: a pilot clinical trial

Abstract

Background: Preclinical research suggests that the efficacy of immune checkpoint inhibitors in breast cancer can be enhanced by combining them with antiangiogenics, particularly in a sequential fashion. We sought to explore the efficacy and biomarkers of combining the anti-PD-L1 durvalumab plus the antiangiogenic bevacizumab after bevacizumab monotherapy for advanced HER2-negative breast cancer.

Methods: Patients had advanced HER2-negative disease that progressed while receiving single-agent bevacizumab maintenance as a part of a previous chemotherapy plus bevacizumab regimen. Treatment consisted of bi-weekly durvalumab plus bevacizumab (10 mg/kg each i.v.). Peripheral-blood mononuclear cells (PBMCs) were obtained before the first durvalumab dose and every 4 weeks and immunophenotyped by flow-cytometry. A fresh pre-durvalumab tumor biopsy was obtained; gene-expression studies and immunohistochemical staining to assess vascular normalization and characterize the immune infiltrate were conducted. Patients were classified as "non-progressors" if they had clinical benefit (SD/PR/CR) at 4 months. The co-primary endpoints were the changes in the percentage T cell subpopulations in PBMCs in progressors versus non-progressors, and PFS/OS time.

Results: Twenty-six patients were accrued. Median PFS and OS were 3.5 and 11 months; a trend for a longer OS was detected for the hormone-positive subset (19.8 versus 7.4 months in triple-negatives; P = 0.11). Clinical benefit rate at 2 and 4 months was 60% and 44%, respectively, without significant differences between hormone-positive and triple-negative (P = 0.73). Non-progressors' tumors displayed vascular normalization features as a result of previous bevacizumab, compared with generally abnormal patterns observed in progressors. Non-progressors also showed increased T-effector and T-memory signatures and decreased TREG signatures in gene expression studies in baseline-post-bevacizumab-tumors compared with progressors. Notably, analysis of PBMC populations before durvalumab treatment was concordant with the findings in tumor samples and showed a decreased percentage of circulating TREGs in non-progressors.

Conclusions: This study reporting on sequential bevacizumab+durvalumab in breast cancer showed encouraging activity in a heavily pre-treated cohort. The correlative studies agree with the preclinical rationale supporting an immunopriming effect exerted by antiangiogenic treatment, probably by reducing TREGs cells both systemically and in tumor tissue. The magnitude of this benefit should be addressed in a randomized setting.

Trial registration: (www.clinicaltrials.gov): NCT02802098 . Registered on June 16, 2020.

Keywords: Bevacizumab; Durvalumab; HER2-negative breast cancer; Immuno-priming; Vascular normalization.

Conflict of interest statement

MQF has received research funds from Astra Zeneca. MQF has received a Research Award from Astra Zeneca Foundation (“Jovenes Investigadores – Cancer 2016”).

Figures

Fig. 1

Trial design. Patients had to be receiving maintenance treatment with bevacizumab alone as a part of a previous bevacizumab-containing regimen for advanced disease, after discontinuing the companion agent because of the usual clinical practice reasons (cumulative toxicity or achievement of maximal disease response). Pre-trial bevacizumab maintenance was allowed at 5 mg/kg weekly, 10 mg/kg q2w, or 15 mg/kg q3w. When patients experienced disease progression while on bevacizumab treatment become candidates for the trial. Bevacizumab treatment was never stopped, and the first durvalumab dose was scheduled for infusion on the next planned bevacizumab dose. All patients switched to a 10 mg/kg weekly bevacizumab schedule in case they were receiving it on a different one. A fresh tumor biopsy was obtained within a time-window of 7 days prior to the first durvalumab dose. In addition, a PBMC sample was obtained on day 1 prior to the first durvalumab dose, and repeated periodically until disease progression; an additional sample was harvested at the end-of-treatment visit (28 days after coming-off trial). Treatment continued until disease progression, unacceptable toxicity or investigator decision

Fig. 2

CONSORT diagram. Twenty six patients underwent trial screening but one patient was deemed ineligible since she was not found to have documented progressive disease to ongoing bevacizumab maintenance. The rest of the patients (N = 25) received at least 1 durvalumab dose and were included in the safety and efficacy analysis. All patients had at least one baseline PBMCs sample for the immune subpopulation analysis; of them, only 6 consented for the pre-treatment tumor biopsy that was subsequently used for immunohistochemistry and gene-expression studies

Fig. 3

Overall efficacy data. a Kaplan-Meier curves (PFS) for the whole population (left) and split by hormonal subtype (TNBC, 2.6 months; hormone-positive, 3.3 months; log-rank P value, 0.84). b Kaplan-Meier curves (OS) for the whole population (left) and split by subtype (TNBC, 7.4 months; hormone-positive, 19.8 months; log-rank P value, 0.11). c Waterfall plot showing best percentage change from baseline in the sum of the longest diameters of target lesions. This plot depicts the changes among the N = 21 patients with measurable disease; the remaining patients (N = 4) had bone disease only (non-measurable but evaluable disease, according to RECIST 1.1). The patient that was non-evaluated due to clinical PD was one of the patients with non-measurable disease. d Swimmer plot depicting the time and durability of response of the 25 patients included in the trial. e Spider plot displaying the longitudinal change from baseline in the sum of the longest diameters of target lesions. It depicts the changes among the same N = 21 patients as in (c). Patients in (c), (d), and (e) are labeled according to their hormonal status: red dot, hormone-positive; black dot, TNBC

Fig. 4

Immune cell sub-populations associated to clinical benefit in peripheral blood mononuclear cells. a Frequency of T-cell subtypes determined by immunophenotyping of PBMC from peripheral blood in non-progressors (red) and progressors (blue) patients in the baseline sample. b Differential Treg percentage in baseline samples among progressors and non-progressors. c Non-progressors displayed a significant increase in central memory—and a trend to increase in effector memory—CD8+ T-cells 4 weeks after the first treatment dose, compared with progressors. d These changes were not evident for CD4+ T cells

Fig. 5

Tumor tissue immunodynamics and gene expression studies suggest immuno-priming by bevacizumab. Representative immunohistochemistry images of a CD8+ infiltration, b CD4+ infiltration, and c Treg infiltration in tumors from non-progressor and progressors patients (upper panels). The lower panels represent the geometric mean and standard deviation of the quantitation data from all available tumor biopsies. d The six analyzed tumors were negative for PD-L1 expression (applying the 1% boundary), regardless of experiencing benefit or not from the treatment combination. e Confocal imaging showing representative fields containing normalized blood vessels from a non-progression (the whole microvessel wall—CD31-positive endothelial cells—is covered by NG2-positive pericytes) and a progressor patient (who, in turn, displays vessel abnormality—lack of pericyte coverage and tortuous architecture). The chart represents the quantitative differences between the average percentage of microvessel wall covered by pericytes in non-progressors versus progressors; **P < 0.01. f Functionally representative GSEAs of the main regulated pathways in non-progressors’ tumors; NES, normalized enrichment score (the higher NES, the higher functional enrichment); both corrected (false discovery ratio (FDR)) and uncorrected P values are shown. g Same as in (f) for non-responders. h Further enriched GSEAs in responders and non-responders ranked by their NES; all of them with FDR < 0.001. Scalebars: a–c 20 μm; d 100 μm; e 25 μm