T-DM1 Efficacy in Patients With HER2-positive Metastatic Breast Cancer Progressing After a Taxane Plus Pertuzumab and Trastuzumab: An Italian Multicenter Observational Study

Long-term hepatobiliary disorder associated with trastuzumab emtansine pharmacovigilance study using the FDA Adverse Event Reporting System database

Trastuzumab emtansine (T-DM1) is widely utilized as a second-line and subsequent treatment for metastatic HER2+ breast cancer and has shown promise in early breast cancer treatment, particularly in adjuvant settings for residual disease after neoadjuvant chemotherapy. However, concerns have arisen regarding long-term hepatic adverse drug reactions (ADRs) not identified in clinical trials. We investigated potential safety signals of T-DM1 in hepatobiliary disorders and the time-to-onset of ADRs using the FDA Adverse Event Reporting System (FAERS) database. Suspected ADRs were extracted and divided into two groups: T-DM1 (N = 3387) and other drugs (N = 11,833,701). Potential signal for T-DM1 in hepatobiliary disorder were identified (reporting odds ratio [ROR] = 5.66, 95% confidence interval [CI] = 5.11-6.27; information component [IC] = 2.35, 95% Credibility Interval [Crl] = 2.18-2.51). A breast cancer indicated subgroup analysis (2519 T-DM1; 172,329 other drugs) also identified a potential safety signal (ROR = 3.28, 95% CI = 2.92-3.68; IC = 1.53, 95%CrI = 1.35-1.71). The median time-to-onset for T-DM1-associated hepatobiliary disorders was 41 days. For prolonged and chronic hepatobiliary disorders, median times were 322.5 and 301.5 days, respectively. These findings highlight the need for further research to inform clinical decisions on optimal T-DM1 treatment duration, balancing benefits with potential adverse reactions.

Real-world data on the efficacy and safety of trastuzumab emtansine in patients with metastatic breast cancer previously treated with pertuzumab: Turkish oncology group multicenter study

We aimed to evaluate the efficacy and safety of trastuzumab emtansine in patients with metastatic breast cancer previously treated with pertuzumab plus trastuzumab and taxane. We reviewed the medical records of patients who were diagnosed with Human Epidermal Growth Factor Receptor 2 (HER-2) positive metastatic breast cancer and received pertuzumab and then TDM-1 between January 2014 and January 2021 from twenty- five cancer centers. The Kaplan- Meier method estimated progression-free survival (PFS) and overall survival (OS). Additionally, objective response rate (ORR), clinical benefit rate (CBR), and safety were evaluated. One hundred fifty-three patients were included,79.1% of the patients received TDM-1 in the second line, 90.8% had visceral metastasis, and 30.7% had central nervous system involvement. The PFS and OS of TDM-1 were evaluated according to the number of previous lines (on the 2nd line or more than two lines) metastatic sites (visceral and non-visceral) and the presence of central nervous metastasis. In TDM-1 therapy, PFS in second line therapy was ten months (95% CI: 7.7 - 12.2); this was statistically higher than later-line PFS, which was six months (95% CI: 3.3 to 8.6) (p = 0.004). The median OS time was 25 months (95% CI: 21.0 to 28.9) in patients treated with TDM-1 in the second line and 19 months (95% CI: 12.3 to 25.6) in patients who received later than the second line(p = 0.175). There were no significant differences in PFS time of patients with and without visceral and central nervous metastases. Our study showed that TDM-1 was also effective in patients using pertuzumab, contributes significantly to PFS when used in the second line compared to its use in the later line, and does not make any difference in OS.

A clinical systematic literature review of treatments among patients with advanced and/or metastatic human epidermal growth factor receptor 2 positive breast cancer

Aim: This systematic literature review aims to summarize the efficacy/effectiveness of treatments, including eribulin (ERI)-based and anti-human epidermal growth factor receptor 2 (HER2) treatments in advanced/metastatic HER2+ breast cancer. Methods: Three databases from 2016 to September 2021 were searched for clinical trials and observational studies in patients receiving first-line (1L) standard of care (SOC), second-line (2L) SOC or third-line or subsequent lines (3L+). Results: 2692 citations were screened, and 38 studies were included. Eleven studies were randomized-controlled trials (RCTs; 5 in 1L, 6 in 3L+), 6 were single-arm trials (5 in 1L, 1 in 3L+) and 21 were observational studies (13 in 1L, 6 in 2L, 4 in 3L+ [note that studies with subgroups for 1L, 2L, 3L+ are double-counted]). Longer overall survival (OS) was associated with 1L and 2L treatment, and for 3L+ studies that included ERI, ERI or trastuzumab (Tmab) + ERI led to longer OS than treatments of physician's choice (median OS of 11, 10 and 8.9 months, respectively). Progression-free survival was 9 months in Tmab + pertuzumab (Pmab) + ERI, 4 months in Tmab + ERI and 3.3 months in ERI. Conclusion: Available treatments provide a wide range of efficacy. However, later lines lack standardization and conclusions on comparative effectiveness are limited by differing trial designs. Thus, the chance of prolonged survival with new agents warrants further research.

NSABP FB-10: a phase Ib/II trial evaluating ado-trastuzumab emtansine (T-DM1) with neratinib in women with metastatic HER2-positive breast cancer

BACKGROUND

We previously reported our phase Ib trial, testing the safety, tolerability, and efficacy of T-DM1 + neratinib in HER2-positive metastatic breast cancer patients. Patients with ERBB2 amplification in ctDNA had deeper and more durable responses. This study extends these observations with in-depth analysis of molecular markers and mechanisms of resistance in additional patients.

METHODS

Forty-nine HER2-positive patients (determined locally) who progressed on-treatment with trastuzumab + pertuzumab were enrolled in this phase Ib/II study. Mutations and HER2 amplifications were assessed in ctDNA before (C1D1) and on-treatment (C2D1) with the Guardant360 assay. Archived tissue (TP0) and study entry biopsies (TP1) were assayed for whole transcriptome, HER2 copy number, and mutations, with Ampli-Seq, and centrally for HER2 with CLIA assays. Patient responses were assessed with RECIST v1.1, and Molecular Response with the Guardant360 Response algorithm.

RESULTS

The ORR in phase II was 7/22 (32%), which included all patients who had at least one dose of study therapy. In phase I, the ORR was 12/19 (63%), which included only patients who were considered evaluable, having received their first scan at 6 weeks. Central confirmation of HER2-positivity was found in 83% (30/36) of the TP0 samples. HER2-amplified ctDNA was found at C1D1 in 48% (20/42) of samples. Patients with ctHER2-amp versus non-amplified HER2 ctDNA determined in C1D1 ctDNA had a longer median progression-free survival (PFS): 480 days versus 60 days (P = 0.015). Molecular Response scores were significantly associated with both PFS (HR 0.28, 0.09-0.90, P = 0.033) and best response (P = 0.037). All five of the patients with ctHER2-amp at C1D1 who had undetectable ctDNA after study therapy had an objective response. Patients whose ctHER2-amp decreased on-treatment had better outcomes than patients whose ctHER2-amp remained unchanged. HER2 RNA levels show a correlation to HER2 CLIA IHC status and were significantly higher in patients with clinically documented responses compared to patients with progressive disease (P = 0.03).

CONCLUSIONS

The following biomarkers were associated with better outcomes for patients treated with T-DM1 + neratinib: (1) ctHER2-amp (C1D1) or in TP1; (2) Molecular Response scores; (3) loss of detectable ctDNA; (4) RNA levels of HER2; and (5) on-treatment loss of detectable ctHER2-amp. HER2 transcriptional and IHC/FISH status identify HER2-low cases (IHC 1+ or IHC 2+ and FISH negative) in these heavily anti-HER2 treated patients. Due to the small number of patients and samples in this study, the associations we have shown are for hypothesis generation only and remain to be validated in future studies. Clinical Trials registration NCT02236000.

New insights into the anticancer therapeutic potential of maytansine and its derivatives

Maytansine is a pharmacologically active 19-membered ansamacrolide derived from various medicinal plants and microorganisms. Among the most studied pharmacological activities of maytansine over the past few decades are anticancer and anti-bacterial effects. The anticancer mechanism of action is primarily mediated through interaction with the tubulin thereby inhibiting the assembly of microtubules. This ultimately leads to decreased stability of microtubule dynamics and cause cell cycle arrest, resulting in apoptosis. Despite its potent pharmacological effects, the therapeutic applications of maytansine in clinical medicine are quite limited due to its non-selective cytotoxicity. To overcome these limitations, several derivatives have been designed and developed mostly by modifying the parent structural skeleton of maytansine. These structural derivatives exhibit improved pharmacological activities as compared to maytansine. The present review provides a valuable insight into maytansine and its synthetic derivatives as anticancer agents.

HER2-Positive Metastatic Breast Cancer: Available Treatments and Current Developments

For several years, the overexpression of the HER2 receptor in breast cancer has been correlated with a poor prognosis and an increased risk of developing brain metastases. Currently, the combination of anti-HER2 double blockade and taxane and trastuzumab emtansine (T-DM1) are considered the standard treatments for metastatic breast cancer overexpressing these receptors in the first and second line. Very recently, the development of a new antidrug conjugate, trastuzumab–deruxtecan, has improved the overall survival of patients, even in second-line treatment. However, trastuzumab–deruxtecan has become a new standard. Despite the benefits of these antidrug conjugates, this benefit in patients with brain metastases remains unclear. Tucatinib is a new tyrosine kinase inhibitor that has given hope for the treatment of these patients. The objective of this article was to review data on the established drugs and novel agents for HER2-positive MBC and to discuss how to incorporate anti-HER2 therapies in first and later-line settings.

Integrin αvβ3 Is a Master Regulator of Resistance to TKI-Induced Ferroptosis in HER2-Positive Breast Cancer

Human epidermal growth factor receptor-2 (HER2)-targeting therapies provide clinical benefits for patients with HER2-positive breast cancer. However, the resistance to monotherapies invariably develops and leads to disease relapse and treatment failure. Previous studies have demonstrated a link between the potency of HER2-targeting tyrosine kinase inhibitors (TKIs) and their ability to induce an iron-dependent form of cell death called ferroptosis. The aim of this study was to understand the mechanisms of resistance to TKI-induced ferroptosis and identify novel approaches to overcome treatment resistance. We used mouse and human HER2-positive models of acquired TKI resistance to demonstrate an intimate link between the resistance to TKIs and to ferroptosis and present the first evidence that the cell adhesion receptor αvβ3 integrin is a critical mediator of resistance to TKI-induced ferroptosis. Our findings indicate that αvβ3 integrin-mediated resistance is associated with the re-wiring of the iron/antioxidant metabolism and persistent activation of AKT signalling. Moreover, using gene manipulation approaches and pharmacological inhibitors, we show that this "αvβ3 integrin addiction" can be targeted to reverse TKI resistance. Collectively, these findings provide critical insights into new therapeutic strategies to improve the treatment of advanced HER2-positive breast cancer patients.

Trastuzumab emtansine vs lapatinib and capecitabine in HER2-positive metastatic breast cancer brain metastases: A real-world study

BACKGROUND

Trastuzumab emtansine (T-DM1) has demonstrated improvements in survival and neurological symptoms in patients with breast cancer with brain metastases (BCBM). This real-world study investigated the effectiveness of T-DM1 versus lapatinib plus capecitabine (LC) in patients with BCBM.

METHODS

This retrospective, observational study evaluated patients with HER2-positive BCBM using a real-world database. Eligible patients had initiated T-DM1 or LC with a prior diagnosis of brain metastasis and ≥1 prior metastatic breast cancer treatment. The primary endpoint was overall survival (OS); secondary endpoints were time to next relevant treatment or death (TTNT) and real-world progression-free survival (rwPFS). An inverse probability of treatment weighting (IPTW) approach was used to account for differences in potential baseline characteristics between treatment groups. Outcomes were described using the Kaplan-Meier method, and the average treatment effect of initiating T-DM1 versus LC was estimated using weighted Cox proportional hazard models and hazard ratio (HR).

RESULTS

A total of 214 patients were available for analysis (T-DM1, n = 161; LC, n = 53). Demographics and baseline characteristics were generally well-balanced between treatment groups after weighting. After weighting, median OS was 17.7 (T-DM1) versus 9.6 (LC) months (HR, 0.55 [95% CI, 0.34-0.89]; P=0.013). Median TTNT was 9.0 (T-DM1) versus 6.0 (LC) months (HR, 0.55 [95% CI, 0.36-0.85]; P = 0.005). After weighting, median rwPFS was 6.0 (T-DM1) versus 4.0 (LC) months (HR, 0.50 [95% CI, 0.36-0.69]; P < 0.001).

CONCLUSIONS

These results support the superior effectiveness and clinical relevance of T-DM1 versus LC in patients with HER2-positive BCBM in the real world.

Antibody drug conjugates targeting HER2: Clinical development in metastatic breast cancer

The identification of the HER2 alteration as an actionable oncogenic driver in breast cancer has propelled the development of HER-targeting monoclonal antibodies (mAb) such as trastuzumab and pertuzumab, which led to dramatic improvements in survival outcomes. Lately, the great strides made toward developing antibody-conjugation methods have led to the development of a new class of compelling compounds, the antibody-drug conjugates (ADCs) targeting HER2 which have profoundly transformed the treatment landscape of breast cancer. HER2-targeting ADCs, trastuzumab-emtansine and trastuzumab-deruxtecan, have improved the overall survival in the second and third-line settings with manageable adverse events. Other HER2-targeting ADCs using novel technological advances in the antibody, linker and/or payload conception have shown promising activity in preclinical and clinical studies and some of them are now being evaluated in larger clinical trials. Multiple challenges still impede the success of ADCs in breast cancer namely the lack of a comprehensive understanding of resistance mechanisms as well as the mechanisms of action of ADCs in special subgroups of patients such as those with low or ultra-low HER2 expression and patients with brain or leptomeningeal metastases (BM). In this framework, we review the approved indications and ongoing trials for HER2-targeting ADCs, across patient subgroups, including those with BM and discuss the associated potential mechanisms of action and resistance. Last, we provide an overview of the future perspectives involving HER2-targeting ADCs in breast cancer.

Final results of the global and Asia cohorts of KAMILLA, a phase IIIB safety trial of trastuzumab emtansine in patients with HER2-positive advanced breast cancer

Background

KAMILLA is a single-arm safety study of trastuzumab emtansine (T-DM1) in patients with human epidermal growth factor receptor 2 (HER2)-positive advanced breast cancer (BC; NCT01702571). We report the final analysis of cohort 2 (Asia) within the context of published cohort 1 (Global) findings.

Methods

Patients had HER2-positive, locally advanced, or metastatic BC progressing after chemotherapy and anti-HER2 therapy or ≤6 months after adjuvant therapy. The primary objective was to further evaluate T-DM1 (3.6 mg/kg, administered intravenously every 3 weeks) safety/tolerability, including the following adverse events of primary interest (AEPIs): grade ≥3 AEPIs (hepatic events, allergic reactions, thrombocytopenia, hemorrhage events), all grade ≥3 treatment-related AEs, and all-grade pneumonitis.

Results

KAMILLA enrolled 2185 patients (cohort 1, n = 2003; cohort 2, n = 182) as of 31 July 2019. Of these, 2002 and 181 per cohort were treated and included in the safety population. Approximately 70% of patients had two or more previous treatment lines in the metastatic setting. Median T-DM1 exposure was 5.6 and 5.0 months per cohort; median follow-up was 20.6 and 15.1 months. The overall AEPI rate was higher in cohort 2 (93/181; 51.4%) versus cohort 1 (462/2002; 23.1%), mostly driven by a higher grade ≥3 thrombocytopenia rate in cohort 2. In cohort 2, grade ≥3 thrombocytopenia was not associated with grade ≥3 hemorrhagic events and most (128/138) fully resolved. Grade ≥3 treatment-related AEPI rates were 18.4% (cohort 1) and 48.6% (cohort 2), the latter mainly due to thrombocytopenia. Any-grade pneumonitis rates were 1.0% and 2.2%. No new safety signals were identified. Median (95% confidence interval) progression-free survival was 6.8 months (5.8-7.6 months) and 5.7 months (5.5-7.0 months) in cohorts 1 and 2, respectively; median overall survival was 27.2 months (25.5-28.7 months) and 29.5 months (21.1 months to non-estimable). In both cohorts, median progression-free survival and overall survival decreased with increasing prior therapy lines.

Conclusions

Cohort 2 results aligned with previous findings in Asian patients, supporting the manageable safety profile and use of T-DM1 in advanced BC.

•

KAMILLA safety results for cohorts 1 (global; n = 2002) and 2 (Asia; n = 181) aligned with results from prior T-DM1 mBC trials.

•

The overall rate of adverse events of primary interest (AEPIs) was higher in cohort 2 (51.4%) versus cohort 1 (23.1%).

•

The higher AEPI rate was mostly due to a higher grade ≥3 thrombocytopenia event rate in cohort 2, most of which resolved.

•

Median PFS and OS were similar for both cohorts, and decreased with increasing prior therapy lines.

•

The manageable safety profile and efficacy of T-DM1 further support its favorable benefit/risk balance.

T-DM1 efficacy in trastuzumab-pertuzumab pre-treated HER2 positive metastatic breast cancer patients: a meta-analysis

Background

Current guidelines consider T-DM1 the standard 2^nd line therapy for HER2 positive metastatic breast cancer (MBC) patients following trastuzumab (T) + pertuzumab (P) and taxane 1^st line treatment. Despite this, there are no prospective studies supporting this sequence.

Methods

We performed a meta-analysis using real world data to determine the efficacy of T-DM1 after 1^st line TP in HER2 positive MBC patients. We used a random-effect model to find differences in the rate of 1-year progression free survival (PFS) between TP pre-treated population and the EMILIA phase III pivotal trial.

Results

Seven studies were eligible. The meta-analysis showed a combined 1-year PFS risk difference for T-DM1 efficacy after TP in 2^nd or more lines of -0.122, with lower and upper limits of -0.253 and 0.010, respectively (p = 0.07), with low heterogeneity among studies (I² 0.01%, p = 0.836). Considering the four studies on T-DM1 in 2^nd line setting, 1-year PFS risk was -0.034 (95% CI -0.207 – 0,139; p = 0.701) (I² 0.01%, p = 0.91).

Conclusion

Overall, the efficacy of T-DM1 after TP seems to be similar to that previously reported in the EMILIA trial. In the second line setting, data are not mature enough to confirm T-DM1 efficacy in TP pre-treated population.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09556-7.

T-DM1 after Pertuzumab plus Trastuzumab: Treatment Sequence-Induced Selection Bias in HER2-Positive Metastatic Breast Cancer

Real-world studies have suggested decreased trastuzumab emtansine (T-DM1) effectiveness in patients with metastatic breast cancer (mBC) who received prior trastuzumab plus pertuzumab (H + P). However, these studies may have been biased toward pertuzumab-experienced patients with more aggressive disease. Using an electronic health record-derived database, patients diagnosed with mBC on/after 1 January 2011 who initiated T-DM1 in any treatment line (primary cohort) or who initiated second-line T-DM1 following first-line H ± P (secondary cohort) from 22 February 2013 to 31 December 2019 were included. The primary outcome was time from index date to next treatment or death (TTNT). In the primary cohort (n = 757), the percentage of patients with prior P increased from 37% to 73% across the study period, while population characteristics and treatment effectiveness measures were generally stable. Among P-experienced patients from the secondary cohort (n = 246), median time from mBC diagnosis to T-DM1 initiation increased from 10 to 14 months (2013-2019), and median TTNT increased from 4.4 to 10.2 months (2013-2018). Over time, prior H + P prevalence significantly increased with no observable impact on T-DM1 effectiveness. Drug approval timing should be considered when assessing treatment effectiveness within a sequence.

Self-Assembly of Oriented Antibody-Decorated Metal-Organic Framework Nanocrystals for Active-Targeting Applications

Antibody (Ab)-targeted nanoparticles are becoming increasingly important for precision medicine. By controlling the Ab orientation, targeting properties can be enhanced; however, to afford such an ordered configuration, cumbersome chemical functionalization protocols are usually required. This aspect limits the progress of Abs-nanoparticles toward nanomedicine translation. Herein, a novel one-step synthesis of oriented monoclonal Ab-decorated metal-organic framework (MOF) nanocrystals is presented. The crystallization of a zinc-based MOF, Zn₂ (mIM)₂ (CO₃ ), from a solution of Zn²⁺ and 2-methylimidazole (mIM), is triggered by the fragment crystallizable (Fc) region of the Ab. This selective growth yields biocomposites with oriented Abs on the MOF nanocrystals (MOF*Ab): the Fc regions are partially inserted within the MOF surface and the antibody-binding regions protrude from the MOF surface toward the target. This ordered configuration imparts antibody-antigen recognition properties to the biocomposite and shows preserved target binding when compared to the parental antibodies. Next, the biosensing performance of the system is tested by loading MOF*Ab with luminescent quantum dots (QD). The targeting efficiency of the QD-containing MOF*Ab is again, fully preserved. The present work represents a simple self-assembly approach for the fabrication of antibody-decorated MOF nanocrystals with broad potential for sensing, diagnostic imaging, and targeted drug delivery.

Updated Austrian treatment algorithm in HER2+ metastatic breast cancer

A group of Austrian breast cancer specialists met in December 2020 to establish a comprehensive clinical benefit-risk profile of available HER2-targeted therapies based on recent data and to develop an updated treatment algorithm by consensus over several months in 2021. A total of four scenarios were developed in which treatment strategies appropriate for specific patient profiles were evaluated. Consensus was established by detailed discussions of each scenario and by reaching full consensus.

Impact of the line of treatment on progression-free survival in patients treated with T-DM1 for metastatic breast cancer

Background

Trastuzumab emtansine (T-DM1) is indicated as second-line treatment for human epidermal growth factor receptor 2 (HER2)-positive metastatic or unresectable locally advanced breast cancer, after progression on trastuzumab and a taxane-based chemotherapy.

We wished to determine if the line of treatment in which T-DM1 is administered has an impact on progression-free survival (PFS) and in particular, if prior treatment with capecitabine/lapatinib or pertuzumab modifies PFS of further treatment with T-DM1.

Patients and methods

We performed a multicenter retrospective study in 3 Belgian institutions. We evaluated PFS with T-DM1 in patients treated for HER2 positive metastatic or locally advanced unresectable breast cancer between January 1, 2009 and December 31, 2016.

Results

We included 51 patients. The median PFS was 9.01 months. The line of treatment in which T-DM1 (1st line, 2nd line, 3rd line or 4+ lines) was administered had no influence on PFS (hazard ratio 0.979, CI95: 0.835–1.143).

There was no significant difference in PFS whether or not patients had received prior treatment with capecitabine/lapatinib (9.17 vs 5.56 months, p-value 0.875).

But, patients who received pertuzumab before T-DM1 tended to exhibit a shorter PFS (3.55 months for T-DM1 after pertuzumab vs 9.50 months for T-DM1 without pretreatment with pertuzumab), even if this difference was not statistically significant (p-value 0.144).

Conclusion

Unlike with conventional chemotherapy, the line of treatment in which T-DM1 is administered does not influence PFS in our cohort of patients with advanced HER2-positive breast cancer.

Ado-trastuzumab for the treatment of metastatic HER2-positive breast cancer in patients previously treated with Pertuzumab

BACKGROUND

Docetaxel in combination with two HER2-directed therapies, trastuzumab and pertuzumab, is the current standard frontline therapy for patients with metastatic HER2-positive breast cancer. Ado-trastuzumab (T-DM1), an antibody-drug conjugate of trastuzumab and a cytotoxic microtubule-inhibitory agent, emtansine, is approved in patients that have progressed with prior trastuzumab-based therapy. However, the benefit of T-DM1 in patients previously treated with pertuzumab therapy for metastatic breast cancer remains unclear.

METHODS

We identified thirty-three adults with metastatic HER2-positive breast cancer treated between March 2013 and July 2018 with T-DM1 either as subsequent therapy after progression on a pertuzumab-based regimen (i.e., "pertuzumab-pretreated") or without prior exposure to pertuzumab (i.e., "pertuzumab-naïve"). Collected data included patient demographics, treatment history, adverse events, and clinical outcomes. For both cohorts receiving T-DM1, the primary endpoint was PFS and secondary endpoints were overall survival (OS), overall response rate (ORR), clinical benefit rate (CBR), and T-DM1-related toxicity rate.

RESULTS

Pertuzumab-pretreated patients (n = 23, with 21 evaluable for T-DM1 efficacy) had a median PFS of 9.5 months (95% CI: 2.9-NA), 1-year OS rate of 67.4% (95% CI: 50.0-90.9%) with an unreached median, ORR of 14.3% (95% CI: 3.0-36.3%), and CBR of 52.4% (95% CI: 29.8-74.3%), with none of these measures being statistically different than those estimated for the pertuzumab-naïve group (n = 10). Treatment with T-DM1 after prior pertuzumab exposure (median T-DM1 duration 2.9 months) resulted in no grade ≥ 3 adverse events.

CONCLUSIONS

In our cohort, prior exposure to pertuzumab did not significantly impact T-DM1's clinical efficacy or safety profile as second- or later-line therapy in patients with metastatic HER2-positive breast cancer.

Current and Future Management of HER2-Positive Metastatic Breast Cancer

Human epidermal growth factor receptor 2 (HER2) is overexpressed and/or amplified in approximately 20% of breast cancers, conferring an aggressive tumor behavior but also an opportunity for targeted therapies. In the advanced setting, the prognosis of patients suffering from this disease has greatly improved after the introduction of new anti-HER2 drugs beyond trastuzumab. For most patients, a taxane combined with trastuzumab and pertuzumab in the first-line setting, followed by trastuzumab-emtansine in second line, should be considered the standard of care today. However, chemo-free anti-HER2 strategies in hormone receptor-positive, HER2-positive breast cancer could also be considered in selected patients. In the third-line setting and beyond, several emerging anti-HER2 therapies are becoming available, including tucatinib, fam-trastuzumab deruxtecan-nxki (DS-8201a), neratinib, and margetuximab-cmkb. In addition, new compounds and combinations are showing promising results in the late-line setting. The treatment landscape of HER2-positive advanced disease is evolving constantly, active drugs such as pertuzumab and trastuzumab-emtansine are moving to early-stage, many biomarkers, including quantification of HER2 itself, are being explored to improve patient selection, and patient populations with specific needs are emerging, such as those with brain metastasis. Here, we provide an overview of the current and future management of HER2-positive advanced breast cancer.

Trastuzumab emtansine for HER2-positive metastatic breast cancer: Outcomes from a whole-of-population Australian cohort

Purpose

We aim to describe the treatment patterns and overall survival (OS) outcomes in patients receiving trastuzumab emtansine (T-DM1) for HER2-positive metastatic breast cancer (HER2+MBC) in routine clinical care.

Methods

Retrospective, whole-of-population cohort study of people initiating T-DM1 for HER2+MBC between October 2015 and May 2019 in Australia. We used dispensing claims to estimate time-to-T-DM1 initiation, duration of treatment, and treatments administered prior to and following T-DM1 therapy. We estimated OS from T-DM1 initiation and stratified results based on whether patients received first- or second-line T-DM1 treatment. We benchmarked outcomes to those reported in the pivotal, EMILIA trial.

Results

345 patients initiated T-DM1: 309 as second-line therapy for HER2+MBC and 36 as first-line therapy. 51% of patients had received endocrine therapy and 98% of second-line patients received pertuzumab prior to starting T-DM1. The median age was 57 years (53 in EMILIA); median time-to-T-DM1 initiation from start of HER2-targeted therapy for HER2+MBC was 11.6 months (IQR: 7.9–16.6); median duration of T-DM1 treatment was 6.5 months (3.1–13.5; 7.6 months in EMILIA), and median OS was 19.3 months (7.9–29.5; 29.9 months in EMILIA).

Conclusions

Our findings highlight differences in patient characteristics (older, more previous pertuzumab therapy) and outcomes (shorter OS) from the T-DM1 pivotal trial and provide real-world estimates that can inform patient, clinician and policy, decisions around the use of HER2-targeted therapies in routine clinical care.

•

Real-world T-DM1 recipients are older than trial participants.

•

Real-world T-DM1 recipients have more prior pertuzumab exposure than trial participants.

•

Median overall survival was 10 months shorter than that reported from the trial.

T-DM1 versus pertuzumab, trastuzumab and a taxane as first-line therapy of early-relapsed HER2-positive metastatic breast cancer: an Italian multicenter observational study

Background

The current standard first-line treatment of human epidermal growth factor receptor 2 (HER2)-positive (+) metastatic breast cancer is the combination of pertuzumab, trastuzumab and a taxane (P + T + taxane), while standard second-line is ado-trastuzumab-emtansine (T-DM1). The registration trial of pertuzumab, however, did not include early-relapsing patients, defined as patients experiencing tumor relapse ≤12 months from the end of (neo)adjuvant anti-HER2 therapy. Conversely, the pivotal trial of T-DM1 included some patients relapsing ≤6 months after the end of (neo)adjuvant trastuzumab. Thus, a proportion of early-relapsing patients are currently eligible to receive T-DM1 as first-line treatment. Nevertheless, no direct comparison exists between the two regimens in this clinical setting.

Patients and methods

We retrospectively compared T-DM1 versus P + T + taxane as first-line treatment in two cohorts of early-relapsing patients in an Italian ‘real-world’ setting, involving 14 public health care institutions. The primary endpoint was progression-free survival. Secondary endpoints included patients' characterization, overall survival and post-progression survival. Univariate and multivariate analyses were carried out. All tests were two-sided and a P ≤ 0.05 was considered statistically significant.

Results

Among 1252 screened patients, 75 met the inclusion criteria. Forty-four (58.7%) received P + T + taxane and 31 (41.3%) received T-DM1. The two cohorts showed similar characteristics of aggressiveness and no significant differences in treatment history. T-DM1, compared with P + T + taxane was associated with worse progression-free survival (adjusted hazard ratio: 2.26, 95% confidence interval: 1.13-4.52, P = 0.021) and overall survival (adjusted hazard ratio: 3.95, 95% confidence interval: 1.38-11.32, P = 0.010), irrespective of previous (neo)adjuvant treatment, age, hormone receptors status, time-to-relapse (≤6 months or within 6-12 months) and presence of visceral/brain metastases. No differences were observed in post-progression survival (P = 0.095).

Conclusions

Our study suggests superiority for P + T + taxane over T-DM1 as up-front treatment of early-relapsing HER2+ metastatic breast cancer, which merits further assessment in larger and prospective trials.

•

This is the first study comparing pertuzumab + trastuzumab + taxane (P + T + taxane) with T-DM1 in early-relapsing HER2+ MBC.

•

The majority of early-relapsing HER2+ MBC have high-grade, node-positive, large primary tumors.

•

First-line T-DM1 compared with P + T + taxane is associated with worse progression-free survival.

•

First-line T-DM1 compared with P + T + taxane is associated with worse overall survival.

•

Post-progression survival does not differ between the two treatments cohorts.

Prolonged Responses With Trastuzumab Emtasine Treatment of Human Epidermal Growth Factor Receptor 2-positive Metastatic Breast Cancer Refractory to Trastuzumab and Pertuzumab: Systematic Review of Evidence

Amplification of human epidermal growth factor receptor 2 (HER2) occurs in around 25% of breast cancers and has been associated with aggressive disease. Here, we summarize published evidence on efficacy and prolonged responses with trastuzumab emtansine (T-DM1) after first-line trastuzumab plus pertuzumab and provide possible factors related to prolonged responses to T-DM1. We conducted a literature search using PubMed, and articles that were published in English between July 1, 2012 and December 31, 2019 were included. A review of the bibliography included in the articles found was made. Nine articles were eligible; 2 were case reports, and the remaining 7 were nonexperimental studies, all retrospective. Five were multi-center works. The total number of patients was 796 (276 received pertuzumab). The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement was used for this systematic review. The population included was heterogeneous among studies according to hormone receptor status, de novo metastatic disease, number of metastatic sites, visceral involvement, brain metastasis, previous neoadjuvant or adjuvant trastuzumab, and line of therapy in which T-DM1 was administered. Less efficacy in terms of responses (overall response rate, 18%-33%) and progression-free survival (4-6 months) with second-line T-DM1, in patients pretreated with pertuzumab, was shown (if compared with the EMILIA trial). The results are more similar to those of the TH3RESA trial (very pretreated population). Prolonged treatments (6 months or more) were observed in at least 17% of cases. The efficacy of T-DM1 after a previous pertuzumab treatment is lower than if pertuzumab is not given, although prolonged responses are observed in this setting.

Trastuzumab emtansine (T-DM1) as adjuvant treatment of HER2-positive early breast cancer: safety and efficacy

Introduction: The prognosis of patients with HER2-positive early breast cancer has radically improved after the introduction of (neo)adjuvant anti-HER2 targeted therapy. Trastuzumab emtansine (T-DM1) is an antibody-drug conjugate combining the anticancer properties of the anti-HER2 agent trastuzumab and the antineoplastic cytotoxic drug DM1. After demonstrating to be an effective and safe treatment for patients with HER2-positive advanced breast cancer, the development of T-DM1 has moved to the early setting.Areas covered: The aim of this review is to explore the current role of T-DM1 in the treatment landscape of HER2-positive early breast cancer, focusing specifically on the efficacy and safety data available in the adjuvant setting.Expert opinion: T-DM1 is an effective and safe treatment option in the adjuvant setting for patients with HER2-positive breast cancer without pathologic complete response after standard neoadjuvant chemotherapy plus anti-HER2 targeted therapy. With the availability of more effective anti-HER2 targeted agents, including T-DM1, there is an urgent need for more chemotherapy de-escalation research efforts in the early setting.

Metastatic Human Epidermal Growth Factor Receptor 2-Positive Breast Cancer: Current Treatment Standards and Future Perspectives

Background

The basis of improved systemic therapy for inoperable or metastatic human epidermal growth factor receptor 2 (HER2)-positive breast cancer is formed by HER2-targeting monoclonal antibodies. Dual HER2 blockade with pertuzumab and trastuzumab in combination with docetaxel in previously untreated patients, and trastuzumab emtansine (T-DM1, an antibody-drug conjugate [ADC] consisting of trastuzumab, a linker and a cytotoxic payload) after prior trastuzumab therapy have demonstrated progression-free survival (PFS) and overall survival (OS) superior to what was achieved with the previous treatment routine. Therefore, pertuzumab and trastuzumab with chemotherapy (preferably with a taxane) and T-DM1 are considered the current standard of care in the first- and second-line settings, respectively. For later lines of therapy, no uniformly recognized standard of care has been defined. Accepted options include treatment with trastuzumab beyond progression, in combination with a broad variety of single-agent chemotherapies used sequentially, or lapatinib (an HER2-targeting tyrosine kinase inhibitor [TKI]) in combination with either trastuzu-mab or capecitabine. However, most of these options have not been formally tested in patients receiving the current standard of care therapy for metastatic disease.

Summary

In patients previously treated with today's standard of care, including a significant subgroup with untreated or progressing brain metastases, the combination of tucatinib, a novel HER2-targeting TKI, with trastuzumab and capecitabine, demonstrates a clinically meaningful improvement in PFS and OS when compared to placebo with trastuzumab and capecitabine. Neratinib, another HER2 TKI, in combination with capecitabine, compared to lapatinib and capecitabine, as well as margetuximab, an HER2-directed monoclonal antibody with a fragment c (Fc) domain engineered to enhance immune activation, compared to trastuzumab, both combined with the investigator's choice of chemotherapy, showed a statistically significantly longer PFS. However, not all patients in the respective trials had received pertuzumab and T-DM1 prior to enrollment and, so far, no improvement in OS has been demonstrated. After a median of 6 prior lines of therapy, trastuzumab deruxtecan (T-DXd), a novel ADC, showed a meaningful overall response and PFS. Although the safety profile was generally manageable, treatment-related interstitial lung disease (ILD) might pose a challenge in routine practice. Pyrotinib, another HER2 TKI, was evaluated in combination with capecitabine in patients after prior exposure to trastuzumab when pertuzumab and T-DM1 were not available. In this setting, PFS was better than with lapatinib and capecitabine.

Key Messages

In 2020, pertuzumab and trastuzumab with taxane-based chemotherapy in the first line, and T-DM1 in the second line, remain the standard of care. Tucatinib, neratinib, margetuximab, and T-DXd expand the armamentarium for treatment beyond the second line. Pyrotinib might be another option, especially for patients, who do not have access to pertuzumab and T-DM1.

Comparative effectiveness of trastuzumab emtansine versus lapatinib plus chemotherapy for HER2+ metastatic breast cancer

Aim: To investigate the comparative effectiveness of trastuzumab emtansine (T-DM1) in a real-world population of HER2+ metastatic breast cancer (mBC) patients. Materials & methods: The Flatiron Health database was used to identify a cohort of HER2+ mBC patients who received first-line trastuzumab treatment and T-DM1 or lapatinib plus chemotherapy as second-line treatment. Overall survival was compared between the two groups. Results: A total of 278 patients with HER2+ mBC received second-line T-DM1 and 34 lapatinib plus chemotherapy. Overall survival was longer in patients treated with T-DM1 than those treated with lapatinib plus chemotherapy (adjusted hazard ratio: 0.56; 95% CI: 0.38-0.85). Conclusion: Real-world data supports the effectiveness of T-DM1 in the second-line treatment of HER2+ mBC patients.

Notch Signaling in Breast Cancer: A Role in Drug Resistance

Breast cancer is a heterogeneous disease that can be subdivided into unique molecular subtypes based on protein expression of the Estrogen Receptor, Progesterone Receptor, and/or the Human Epidermal Growth Factor Receptor 2. Therapeutic approaches are designed to inhibit these overexpressed receptors either by endocrine therapy, targeted therapies, or combinations with cytotoxic chemotherapy. However, a significant percentage of breast cancers are inherently resistant or acquire resistance to therapies, and mechanisms that promote resistance remain poorly understood. Notch signaling is an evolutionarily conserved signaling pathway that regulates cell fate, including survival and self-renewal of stem cells, proliferation, or differentiation. Deregulation of Notch signaling promotes resistance to targeted or cytotoxic therapies by enriching of a small population of resistant cells, referred to as breast cancer stem cells, within the bulk tumor; enhancing stem-like features during the process of de-differentiation of tumor cells; or promoting epithelial to mesenchymal transition. Preclinical studies have shown that targeting the Notch pathway can prevent or reverse resistance through reduction or elimination of breast cancer stem cells. However, Notch inhibitors have yet to be clinically approved for the treatment of breast cancer, mainly due to dose-limiting gastrointestinal toxicity. In this review, we discuss potential mechanisms of Notch-mediated resistance in breast cancer cells and breast cancer stem cells, and various methods of targeting Notch through γ-secretase inhibitors, Notch signaling biologics, or transcriptional inhibitors. We also discuss future plans for identification of novel Notch-targeted therapies, in order to reduce toxicity and improve outcomes for women with resistant breast cancer.

The role of ado-trastuzumab emtansine in current clinical practice

OBJECTIVE

This review reflects the literature from 2019 to 2020 on ado-trastuzumab emtansine's (T-DM1) therapeutic use, clinical controversies, and newest perspectives on use.Data sources: PubMed was used as a database. Search "ado-trastuzumab emtansine" on June 11th, 2020 resulted in 57 publications: 20 clinical trials, two metanalysis, six randomized controlled studies, 13 reviews, and two systematic reviews. Of the 57 publications, 34 were descriptive of the topic in question and were used for this review.Data summary: T-DM1 is now used for patients with HER2 breast cancer who have residual disease post surgery after neoadjuvant chemotherapy (KATHERINE trial). Initial success prompted KRISTINE trial, which investigated whether T-DM1 can be used as a neoadjuvant therapy. While it did have fewer adverse events, T-DM1 was inferior to chemotherapy in treating early breast cancer. Noted shortcomings of the drug were toxicity limited C_max, slow rate of internalization, lack of payload bystander effects, and number of resistance mechanisms. Proposed solutions were pre-treatment with metformin to augment drug internalization by the cell, use of second generation anti-HER2 antibody-drug conjugates to overcome developing resistance, payload swapping to increase bystander effect.

CONCLUSIONS

While T-DM1 has fewer side-effects, it is inferior to chemotherapy in early breast cancer treatment. More research should be done to overcome resistance pathways, identify rate-limiting intracellular processing pathways, improve bystander, and enhance internalization of the drug. Until more research is done, T-DM1 will continue to be used in HER2 positive breast cancer as well as a few other HER2 expressing tumors that fail to respond to neoadjuvant therapy.

Systemic therapy for metastatic HER2-positive breast cancer

The human epidermal growth factor receptor 2 (HER2), is amplified and/or overexpressed in approximately 15%-20% of breast cancers. Targeting of the HER2 receptor with the humanized monoclonal antibody trastuzumab in combination with chemotherapy has become the backbone of treatment for both early stage and metastatic breast cancer for the last 2 decades. Relapsed or de novo metastatic HER2-positive breast cancer essentially remains an incurable disease. Nonetheless, with advances in therapeutics, survival rates in this group continue to increase with median survival now in excess of 57 months. First line systemic therapy for HER2-positive metastatic breast cancer using taxane chemotherapy combined with trastuzumab and pertuzumab, and second line therapy with trastuzumab emtansine, are well established. Recent studies of small molecule oral tyrosine kinase inhibitors such as tucatinib and neratinib, and antibody drug conjugates such as trastuzumab deruxtecan further improve outcomes. Major treatment challenges remain in the areas of brain metastases and development of drug resistance. This review details an up to date analysis of current and emerging treatments of metastatic HER2-positive breast cancer.

Second line trastuzumab emtansine following horizontal dual blockade in a real-life setting

Despite relevant medical advancements, metastatic breast cancer remains an uncurable disease. HER2 signaling conditions tumor behavior and treatment strategies of HER2 expressing breast cancer. Cancer treatment guidelines uniformly identify dual blockade with pertuzumab and trastuzumab plus a taxane as best first line and trastuzumab emtansine as preferred second line choice. However, there is no prospectively designed available study focusing on the sequence and outcomes of patients treated with T-DM1 following the triplet. In the following report, data concerning a wide series of patients treated in a real-life setting are presented. Results obtained in terms of response and median progression free survival suggests a significant role for T-DM1 in disease control of metastatic HER2 expressing breast cancer.