HER2 Tyrosine Kinase Research Articles

1246P Multicenter phase Ib/II study of second-line varlitinib and paclitaxel in patients with EGFR/HER2 co-expressing advanced gastric cancer (K-MASTER-13)

Varlitinib is a small-molecule inhibitor of the tyrosine kinases EGFR, HER2, and HER4. We present a phase Ib/II study to evaluate the safety and efficacy of varlitinib in combination with weekly paclitaxel in EGFR/HER2 co-expressing advanced gastric cancer (AGC) patients. (KCT0003583). AGC patients who had failed 1st line fluoropyrimidine-containing chemotherapy, with evidence of both EGFR and HER2 overexpression by IHC (≥1+), were enrolled. Varlitinib [Dose 1: 300 mg BID, Dose -1: 300mg intermittent dose] and paclitaxel (80 mg/m2 D1,8,15) were investigated every 4 weeks. After determining the DLT and RP2D in phase Ib, phase II part was conducted to evaluate the anti-tumor activity with a primary endpoint of PFS. In the phase Ib study, 9 subjects were enrolled at the dose 1 level of varlitinib 300mg, of which 6 patients were evaluable for safety per protocol. Among the 6 evaluable patients, there was 1 DLT of Grade 4 AST/ALT elevation. The RP2D was varlitinib 300mg once daily combined with paclitaxel (80mg/m2 on days 1, 8, and 15). The median follow-up duration of 9.3 months [95% confidence interval (CI), 6.1-12.5]. Among 27 patients treated with RP2D including 5 subjects from Phase Ib, median PFS and OS were 4.1 (95% CI, 2.4-4.9 months) and 7.9 months (95% CI, 3.3-12.5 months), respectively. Among 16 patients with measurable disease and administered with RP2D, confirmed response and disease control was observed in 5 patients (ORR=31.3%) and 14 patients (DCR=87.5%), respectively. No definite association between EGFR or HER2 high expression and the efficacy of varlitinib and paclitaxel could be determined. Most common any grade of adverse events (AEs) were neutropenia (51.8% and 22.2% of Grade 3), diarrhea (27.3%), and AST/ALT elevation (22.2% and 11.1% of Grade 3). No treatment related death or unexpected AEs resulting in treatment cessation were observed with the RP2D. Varlitinib combined with paclitaxel revealed manageable toxicities and antitumor activity in patients with EGFR/HER2 co-expressing AGC who progressed after first-line chemotherapy. Updated outcomes for ongoing patients and biomarker analysis will be presented.

239P Pyrotinib in combination with docetaxel as first-line treatment for HER2-positive metastatic breast cancer (PANDORA): A single-arm, multicenter phase II trial

Pyrotinib is a small molecule tyrosine kinase inhibitor targeting HER1, HER2, and HER4. The phase III PHOEBE trial has proved its superiority over lapatinib when in combination with capecitabine in previously treated, HER2-positive metastatic breast cancer. This phase II trial aimed to investigate the activity of pyrotinib plus docetaxel as first-line treatment in HER2-positive metastatic breast cancer.

238P Clinical safety and pharmacokinetics (PK) data of DZD1516, an BBB-penetrant selective HER2 inhibitor for the treatment of HER2-positive metastatic breast cancer

Patients with HER2-positive (+) metastatic breast cancer (MBC) are at high risk of developing central nervous system (CNS) metastases. DZD1516 is designed as a reversible and selective HER2 tyrosine kinase inhibitor (TKI) with full blood-brain barrier (BBB) penetration.

Synthesis and in vitro anticancer activity of 4H-pyrano[2,3-d]pyrimidine−1H-1,2,3-triazole hybrid compounds bearing D-glucose moiety with dual EGFR/HER2 inhibitory activity and induced fit docking study

• 4 H -Pyrano[2,3- d ]pyrimidine−1,2,3-triazole− d -glucose hybrid compoundssynthesized • Some compounds inhibited for MCF7, HepG2, HeLa cell lines with IC 50 < 4 μM • Compounds 8v,8z,8zc , and 8zf exhibited against EGFR and HER2 tyrosine kinases • Induced fit docking and MM-GBSA simulations for 8zc on EGFR enzyme. The polysubstituted 4 H -pyrano[2,3- d ]pyrimidines 6a-zj containing propargyl group on nitrogen atom 3 of ring have been synthesized by ring-closing reaction of corresponding 2-amino-3-cyano-4 H -pyrans 4a-zj with acetic anhydride and trifluoroacetic acid as catalyst, followed by alkylation with propargyl bromide under ultrasound conditions. A series of 36 analogs of 4 H -pyrano[2,3- d ]pyrimidine 8a-zj bearing d -glucose moiety tethered 1,2,3-triazole derivatives, including eighteen new ones, were synthesized by click chemistry between these N -propargyl derivatives and peracetylated d -glucopyaranosyl azide, with using CuNPs@Montmorillonite as a catalyst under ultrasound condition in the presence of DIPEA in t -BuOH/H 2 O at 25°C for 20 min. These compounds exhibited potent anticancer activity against tested cancer cells, including MCF-7, HepG2, and HeLa. Amongst tested compounds, some compounds exhibited strong activity against tested cancer cell lines with IC 50 < 4 μM, such as 8v,8x,8z,8zc,8zf and 8zg against MCF-7, 8s,8t,8w,8zh , and 8zi against HepG2, 8h,8j,8zf and 8zh against HeLa cancer cell lines. Compounds 8v,8z,8zc , and 8zf exhibited remarkable inhibitory activity against EGFR and HER2 tyrosine kinases in comparison with Lapatinib. The resulted docking studies showed that compound 8zc displayed binding mode like Erlotinib on EGFR enzyme and showed good binding energies. Induced fit docking, MM-GBSA calculation, and molecular dynamics simulations were carried out to elucidate the inhibitory potential of compound 8zc against tested enzyme 4HJO. Docking analysis showed that amongst the hydrophilic and hydrophobic interactions at the active site of EGFR enzyme, the hydrogen-bond bindings between acetate function and appropriate amino acid residues displayed the most important contribution in intensifying their potency against this enzyme.

Association of ERBB2 Copy Number and Gene Coalterations With Trastuzumab Efficacy and Resistance in Human Epidermal Growth Factor Receptor 2-Positive Esophagogastric and Gastric Cancer.

PURPOSEERBB2 copy number (CN), measured using next-generation sequencing, is a predictive biomarker for trastuzumab efficacy in human epidermal growth factor receptor 2 (HER2)–positive advanced esophagogastric and gastric cancer (AGC). We aimed to investigate the association of ERBB2 amplification and gene coalterations with response and resistance to trastuzumab-combined chemotherapy.METHODSThe SCRUM-Japan GI-SCREEN was a comprehensive genomic profiling project of GI cancer tissues using Oncomine Cancer Research Panel and Oncomine Comprehensive Assay. From 885 patients with AGC who successfully underwent gene profiling, 74 with ERBB2 amplification (CN ≥ 4.0) and who received first-line trastuzumab-combined chemotherapy were selected, and ERBB2 CN and gene coalterations were assessed.RESULTSERBB2 CN did not differ in tumor response to trastuzumab-combined chemotherapy (one-way analysis of variance test, P = .37). Multivariate analysis using the Cox proportional hazard model revealed that ERBB2 CN (continuous log2-converted CN, hazard ratio, 0.76; 95% CI, 0.62 to 0.93; P < .01) and receptor/oncogene amplifications in the HER2 signaling pathway (hazard ratio, 2.5; 95% CI, 1.2 to 5.3; P = .01) were significant predictors for progression-free survival (PFS). ERBB2 variants coexisted in five patients (7%) and were missense mutations. Two patients with low variant allele frequencies (VAFs; 8%, 12%) showed high ERBB2 CN (55, 80) and durable response (≥ 20 months), whereas three patients with high VAFs (66%–90%) showed low ERBB2 CN (8-11) and no response with short PFS (1-10 months).CONCLUSIONERBB2 CN and gene coamplification in the HER2 signaling pathway were positive and negative predictors of PFS in trastuzumab-treated HER2-positive AGC patients, respectively. HER2-positive AGC patients with a high VAF of ERBB2 showed poor outcomes and may need HER2 tyrosine kinase inhibitors and trastuzumab deruxtecan.

Current updates on EGFR and HER2 tyrosine kinase inhibitors for the breast cancer

Current updates on EGFR and HER2 tyrosine kinase inhibitors for the breast cancer

Abstract 5661: HER2 inhibition increases non-muscle myosin IIa to promote tumorigenesis in HER2+ breast cancers

Abstract HER2 is amplified in about 20% of breast cancers. HER3 is as essential as HER2 for maintaining cell viability in HER2+ breast cancer cells. It is known that inhibition of HER2 tyrosine kinase activity results in upregulation of HER3 transcription and phosphorylation. We sought to identify HER3 binding partners upon pharmacological inhibition of HER2 using neratinib. We immunoprecipitated HER3 using a HER3 antibody from BT474 cells treated ± neratinib. Fmass spectrometry experiments identified non-muscle myosin IIA (NMIIA) increased upon inhibition of HER2 with neratinib and decreased under DMSO control treatment from HER3 immunoprecipitates. To validate the presence of NMIIA, we performed immunoprecipitation experiments in BT474 and MDA-MB-453 cells using a HER3 antibody. Immunoblots showed increased NMIIA levels upon treatment with 200nM neratinib for 24 hours in both cell lines. Myosin heavy chain 9 (MYH9) gene encodes a protein called non-muscle myosin of class II, isoform A (NMIIA). It localizes to actin stress fibers and has been implicated in many cell functions. To confirm the interaction between HER3 and NMIIA we immunoprecipitated NMIIA from BT474 and MDA-MB-453 cells using a NMIIA antibody. Immunoblots indicated that HER3 levels were increased upon inhibition of HER2 with 200 nM neratinib for 24 hours. We next examined overall survival of primary breast cancer patients who have high gene expression for MYH9 from the METABRIC cohort. We observed that patients with high levels of MYH9 have a statistically significant worse overall survival versus patients with low levels of MYH9. Furthermore, we evaluated the overall levels of HER3 and MYH9 mRNA and protein upon treatment with neratinib in BT474 and MDA-MB-453 whole cell lysates. RT-qPCR and immunoblots showed increased HER3 and NM-IIA mRNA and protein levels upon neratinib treatment for 24 hours We examined the affect NMIIA loss has on HER3 signaling. Transduced MDA-MB-453 and BT474 cells with shMYH9 and doxycycline induction demonstrate a reduction in HER3 protein levels compared to cells transduced with a control sequence and doxycycline induction. We observed a concomitant reduction in P-HER3 (Y1289), downstream P-Akt (T308), and P-Erk1/2. In addition, NM-IIA knockdown suppresses cells growth, proliferation, migration, and invasion. In conclusion, there is a bidirectional relationship between NMIIA and HER signaling in HER2+ breast cancer cells. HER2 inhibition increases NMIIA and NMIIA promotes HER3 expression. Loss of NMIIA reduces HER3 protein and concomitant reductions in PI3K/Akt and MAPK signaling. Loss of NMIIA in combination with HER2 inhibition results in reduction in HER2+ breast cancer cell proliferation, growth on matrigel, migration, and invasion. Studies are ongoing to decipher the mechanisms for the bidirectional relationship between NMIIA and HER signaling. Citation Format: Samar M. Alanazi, Rosalin Mishra, Hima Patel, Mary K. Kilroy, Joan T. Garrett. HER2 inhibition increases non-muscle myosin IIa to promote tumorigenesis in HER2+ breast cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5661.

Abstract 5412: Role of her3 mutations on breast cancer oncogenesis

Abstract We sought to determine if naturally occurring mutations in HER3 could drive oncogenic growth of HER3KO HER2+ HCC1569 cells in which endogenous HER3 has been eliminated via CRISPR-Cas9. A series of HER3 mutations identified in breast cancer patients (F94L, V104L, G284R, D297Y, T355I, and E928G) were introduced using lentiviral transduction and stable cell lines were generated in HER3KOHCC1569 cells via puromycin selection. We identified HER3V104L mutation to have higher cell proliferation and higher p-HER3 expression compared to wild-type (wt) and empty-vector (EV) HER3. We observed that HCC1569HER3KO cells stably expressing WT and V104L were sensitive to increasing doses of neratinib (0.1-0.5 µM) concentration. Next we analyzed if this mutation rendered resistance to the recently FDA- approved irreversible HER2 tyrosine kinase inhibitor, tucatinib. Our data indicated that both that V104L cells were sensitive to higher concentration of tucatinib compared to neratinib. In parallel experiments, we utilized COS7 cells to examine the signaling properties of HER3V104L. Our data indicated that transient transfection of COS7 cells with HER3V104L mutant significantly induces p-HER3/p-AKT and p-HER2 expression compared to WT HER3 in a ligand dependent manner. In addition, we observed that the V104L mutation stabilizes HER3 protein expression independent of HER2 and ligand stimulation. Experiments are ongoing to determine whether V104L induced HER3 stabilization and downstream signaling activation is dependent on HER3 binding partners including EGFR, HER2 or HER4. We also aim to understand how the V104L mutation stabilizes HER3 expression. Structural modeling of V104L mutation will provide insight about the mechanism of stabilization of the HER3 protein. We will use MCF10A and HEK293 cells to determine the effect of the V104L mutation on HER3 expression and downstream signaling. We also aim to decipher the signaling mechanism that drives the oncogenic potential of V104L mutation. In addition, we are using various PDXs with different HER3 mutations to determine other driver HER3 mutations in breast cancer and how this can be targeted in the clinic using HER targeted therapy. Citation Format: Rosalin Mishra, Mary Kate Kilroy, Hima Patel, Samar Alanazi, Joan T. Garrett. Role of her3 mutations on breast cancer oncogenesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5412.

Depleting receptor tyrosine kinases EGFR and HER2 overcomes resistance to EGFR inhibitors in colorectal cancer

BackgroundEpidermal growth factor receptor (EGFR) inhibitors, including cetuximab and panitumumab, are valuable therapeutics for colorectal cancer (CRC), but resistance to these inhibitors is common. The reason for such resistance is not well understood, which hampers development of better therapeutic strategies. Although activating mutations in KRAS, BRAF and PIK3CA are considered major drivers of CRC resistance to EGFR inhibitors, therapeutic targeting of these drug resistance drivers has not produced substantial clinical benefit.MethodsWe exploited cell lines and mouse tumor models (cell line xenografts and patient derived xenografts) for experiments of genetic and pharmacologic depletion of EGFR and/or its family member HER2, including EGFR mutants, inhibition of EGFR ligand shedding, and biochemical analysis of signaling proteins, to delineate the mechanism of CRC resistance to EGFR inhibitors and to assess the therapeutic activity of PEPDG278D, which is a recombinant human protein that induces the degradation of both EGFR and HER2.ResultsThe sensitivity of CRC cells to cetuximab and panitumumab correlates with the ability of these drugs to induce EGFR downregulation. PEPDG278D strongly inhibits oncogenic signaling and growth of CRC cells by causing profound depletion of EGFR and HER2, regardless of activating mutations of KRAS, BRAF and PIK3CA. siRNA knockdown of EGFR or HER2 also inhibits CRC cells resistant to EGFR inhibitors. Tumors harboring mutated KRAS, BRAF and/or PIK3CA also overexpress EGFR ligands, further suggesting that EGFR signaling remains important to the tumors. While excessive tumor-generated high-affinity EGFR ligands block target engagement by PEPDG278D, aderbasib, an inhibitor of ADAM10 and ADAM17, enables PEPDG278D to exert strong antitumor activity by inhibiting ligand shedding. Moreover, adding fluorouracil, which is commonly used in CRC treatment, to the combination of PEPDG278D and aderbasib further enhances tumor inhibition.ConclusionsOur study shows that CRC resistance to EGFR inhibitors results primarily from the inability of the inhibitors to downregulate their target and that a PEPDG278D-based combination treatment overcomes the resistance.

Mechanistic Modeling of Central Nervous System Pharmacokinetics and Target Engagement of HER2 Tyrosine Kinase Inhibitors to Inform Treatment of Breast Cancer Brain Metastases.

This study evaluated the central nervous system (CNS) pharmacokinetics and target engagement of lapatinib, neratinib, and tucatinib in patients with cancer, using a physiologically based pharmacokinetic (PBPK) modeling approach. Drug-specific parameters for in vitro metabolism, binding to plasma proteins and brain tissues, transcellular passive permeability, and interactions with efflux transporters were determined. Whole-body PBPK models integrated with a 4-compartment permeability-limited brain model was developed and verified for predicting plasma and CNS pharmacokinetics. Target engagement ratio (TER), defined as the ratio of the average steady-state unbound drug brain concentration (Css,ave,br) to in vitro IC50 for HER2 inhibition, was used as a predictor of intracranial efficacy. PBPK models predicted that following 1 cycle of standard dosing, tucatinib and lapatinib achieved similar Css,ave,br (14.5 vs. 16.8 nmol/L), while neratinib Css,ave,br (0.68 nmol/L) was 20-fold lower. Tucatinib and neratinib were equally potent for HER2 inhibition (IC50, 6.9 vs. 5.6 nmol/L), while lapatinib was less potent (IC50, 109 nmol/L). The model-predicted population mean TER in the human normal brain was 2.1 for tucatinib, but < 0.20 for lapatinib and neratinib. The PBPK modeling suggests that tucatinib induces sufficient HER2 inhibition (TER > 2.0) in not only brain metastases with a disrupted blood-brain barrier (BBB), but also micrometastases where the BBB largely remains intact. These findings, in line with available clinical pharmacokinetics and efficacy data, support the therapeutic value of tucatinib for treatment of brain metastases and warrant further clinical investigation for the prevention of brain metastases in patients with HER2-positive breast cancer.

Molecular Docking Studies of Glabrene and Human Epidermal Growth Factor Receptor Kinase

Background: Human epidermal growth factor receptor 2 (Her2) gene located in human chromosome17, encodes Her2 tyrosine kinase protein, and is overexpressed in breast cancer cells. Her2 is activated on phosphorylation of tyrosine by adenosine triphosphate (ATP). Nonetheless, Her2 excessively partakes in the development and prognosis of specific types of aggressive breast cancers. Therefore, Her2 inhibition therapy is primary target for the treatment of aggressive breast cancer. At present, lapatinib is one of the Food and Drug Administration approved Her2 inhibitors used in cancer therapy. In molecular docking process, glabrene with slightly higher binding energy competitively bound to the active receptor site comparable to lapatinib and ATP. Therefore, glabrene could emerge as a potential candidate for restricting Her2 overexpressed breast cancer.&#x0D; Objective: The present study aimed to demonstrate the inhibitory activity of glabrene, an isoflavene and xenoestrogen found in liquorice root, along with known Her2 inhibitor, lapatinib.&#x0D; Methods: ATP, lapatinib, and glabrene were docked on human Her2 protein 3D structure which revealed glabrene as a competitive Her2 inhibitor akin to lapatinib. Results: The docking results suggested the binding site similarities of ATP, lapatinib, and glabrene. The binding energies of docked ATP, lapatinib, and glabrene complexes with Her2 were −9.1 kcal/mol, −10.5 kcal/mol, and −11.3 kcal/mol, respectively.&#x0D; Conclusion: The in silico docking simulation of ATP, lapatinib, and glabrene suggested that glabrene is likewise a competitive Her2 inhibitor.

DESIGN AND SYNTHESIS OF DUAL HER-2 AND PI3 KINASE INHIBITORS FOR THE TREATMENT OF BREAST CANCER: A MULTIDIMENSIONAL APPROACH

Breast cancer is the most commonly found cancer in women and the incidence is high in developing countries. Very few HER-2 tyrosine kinase inhibitors available in the market, but chronic use of some of these inhibitors may result in resistant to the treatment. The dual inhibition of HER-2 and PI3K tyrosine kinases can effectively treat breast cancers. In view of this, the present investigation is directed to the design of dual HER-2 and PI3K inhibitors employing a multidimensional drug design approach. In this approach, molecular docking studies of some existing HER-2 and PI3K inhibitors were carried out and physicochemical properties were also considered to identify common structural features for dual inhibition. From these results, new dual HER-2 and PI3K inhibitors were designed. Among some of the designed molecules new thienopyrimidines were synthesized and tested for anti-proliferative activity on breast cancer cell lines. Finally, six heterocyclic core moieties and important substituents were identified for HER-2 and PI3K selectivity. Among them thienopyrimidine was selected for the synthesis. Some of the synthesized compounds were found to show appreciable anti-proliferative activity in the in vitro cytotoxicity studies.

Dalpiciclib Combined With Pyrotinib and Letrozole in Women With HER2-Positive, Hormone Receptor-Positive Metastatic Breast Cancer (LORDSHIPS): A Phase Ib Study.

PurposeThe LORDSHIPS study aimed to explore the safety and efficacy of a novel fully oral triplet combination of dalpiciclib (a potent cyclin-dependent kinase 4/6 inhibitor), pyrotinib (a HER2 tyrosine kinase inhibitor) and endocrine therapy letrozole in patients with HER2-positive, hormone receptor (HR)-positive metastatic breast cancer (MBC) in the front-line setting.Patients and MethodsPostmenopausal women with HER2-positive, HR-positive MBC were recruited in the dose-finding phase Ib trial. A standard 3 + 3 design was used to determine safety, tolerability, and recommended phase II dose (RP2D) for the combination.ResultsA total of 15 patients were enrolled to three dose combination cohorts (letrozole/pyrotinib/dalpiciclib, level/I: 2.5/400/125 mg, n=5; level/L1: 2.5/400/100 mg, n=6; level/L2: 2.5/320/125 mg, n=4). Three patients experienced dose-limiting toxicities (level/I, n=2; level/L1, n=1) and level/L2 was identified as RP2D. The most frequent grade 3-4 adverse events were neutropenia (46.7%), leukopenia (40.0%), oral mucositis (26.7%) and diarrhea (20.0%). The confirmed objective response rate (ORR) was 66.7% (95% CI: 38.4% to 88.2%). The confirmed ORR of study treatment as first line (1L) and second line (2L) HER2-targeted therapy was 85.7% (6/7) and 50.0% (4/8), respectively. Median progression-free survival (PFS) was 11.3 months (95% CI: 5.3 months to not reached). PFS in 1L setting was not reached yet, while PFS in 2L setting was 10.9 months (95% CI: 1.8 to 13.7 months).ConclusionsThe fully oral combination of dalpiciclib, pyrotinib and letrozole is a promising chemotherapy-sparing treatment option for HER2-positive, HR-positive MBC patients. The planned dose-expansion phase II study is ongoing.Clinical Trial Registration ClinicalTrials.gov, identifier NCT03772353.

Pharmacotranscriptomic profiling of resistant triple-negative breast cancer cells treated with lapatinib and berberine shows upregulation of PI3K/Akt signaling under cytotoxic stress.

Triple-negative breast cancer (TNBC) is the most incurable type of breast cancer, accounting for 15-20% of breast cancer cases. Lapatinib is a dual tyrosine kinase inhibitor targeting EGFR and Her2, and berberine (BBR) is a plant-based alkaloid suggested to inhibit several cancer signaling pathways. We previously reported that lapatinib activates the Akt oncoprotein in MDA-MB231 TNBC cells. The present study determined the mechanism(s) of Akt activation in response to lapatinib, BBR, and capivasertib (Akt inhibitor) as well as the role of Akt signaling in chemoresistance in TNBC cells. Genetic profiles of 10 TNBC cell lines and patients were analyzed using datasets obtained from Gene Expression Omnibus and The Cancer Genome Atlas Database. Then, the effects of lapatinib, BBR, and capivasertib on treated MDA-MB231 and MCF-7 cell lines were studied using cytotoxicity, immunoblot, and RNA-sequencing analyses. For further confirmation, we also performed real-time PCR for genes associated with PI3K signaling. MDA-MB231 and MCF-7 cell lines were both strongly resistant to capivasertib largely due to significant Akt activation in both breast cancer cell lines, while lapatinib and BBR only enhanced Akt signaling in MDA-MB231 cells. Next-generation sequencing, functional enrichment analysis, and immunoblot revealed downregulation of CDK6 and DNMT1 in response to lapatinib and BBR lead to a decrease in cell proliferation. Expression of placental, fibroblast growth factor, and angiogenic biomarker genes, which are significantly associated with Akt activation and/or dormancy in breast cancer cells, was significantly upregulated in TNBC cells treated with lapatinib and BBR. Lapatinib and BBR activate Akt through upregulation of alternative signaling, which lead to chemoresistance in TNBC cell. In addition, lapatinib overexpresses genes related to PI3K signaling in resistant TNBC cell model.

Triple Targeting of HER Receptors Overcomes Heregulin-mediated Resistance to EGFR Blockade in Colorectal Cancer.

Current treatment options for patients with advanced colorectal cancers include anti-EGFR/HER1 therapy with the blocking antibody cetuximab. Although a subset of patients with KRAS WT disease initially respond to the treatment, resistance develops in almost all cases. Relapse has been associated with the production of the ligand heregulin (HRG) and/or compensatory signaling involving the receptor tyrosine kinases HER2 and HER3. Here, we provide evidence that triple-HER receptor blockade based on a newly developed bispecific EGFR×HER3-targeting antibody (scDb-Fc) together with the HER2-blocking antibody trastuzumab effectively inhibited HRG-induced HER receptor phosphorylation, downstream signaling, proliferation, and stem cell expansion of DiFi and LIM1215 colorectal cancer cells. Comparative analyses revealed that the biological activity of scDb-Fc plus trastuzumab was sometimes even superior to that of the combination of the parental antibodies, with PI3K/Akt pathway inhibition correlating with improved therapeutic response and apoptosis induction as seen by single-cell analysis. Importantly, growth suppression by triple-HER targeting was recapitulated in primary KRAS WT patient-derived organoid cultures exposed to HRG. Collectively, our results provide strong support for a pan-HER receptor blocking approach to combat anti-EGFR therapy resistance of KRAS WT colorectal cancer tumors mediated by the upregulation of HRG and/or HER2/HER3 signaling.

Abstract PD8-07: Evaluation of Tucatinib + (Paclitaxel + Pertuzumab + Trastuzumab) followed by AC in high-risk HER2 positive (HER2+) stage II/III breast cancer: Results from the I-SPY 2 TRIAL

Abstract Background: I-SPY 2 is a multicenter, phase 2 trial using response-adaptive randomization within molecular subtypes defined by receptor status and MammaPrint (MP) risk to evaluate novel agents as neoadjuvant therapy for women with high-risk breast cancer. Tucatinib is a potent HER2 (ErbB2) tyrosine kinase inhibitor, selective for HER2 vs. epidermal growth factor receptor (EGFR) and is active vs. brain metastases. Safety and efficacy of tucatinib combined with paclitaxel, pertuzumab, and trastuzumab are unknown and were tested in a planned 10 patient (pt) safety run-in of the I-SPY 2 trial. Methods: Women with tumors ≥ 2.5cm were eligible for screening. Only pts with tumors that were HER2+ by FISH were eligible for this treatment. Treatment included tucatinib (max dose 300 mg) BID for 12 weeks with weekly paclitaxel 80 mg/m2 and trastuzumab (2 mg/kg weekly following loading), and pertuzumab (420 mg every 3 weeks following loading), followed by doxorubicin/cyclophosphamide (AC) every 2 weeks x 4. The control arm was weekly paclitaxel and trastuzumab with pertuzumab for 12 weeks followed by AC every 2 weeks x 4. All pts undergo serial MR imaging and response at 3 &amp; 12 weeks is combined with real time pCR data to estimate, and continuously update, the predicted pCR rate for each trial arm. The goal of the trial is to identify/graduate regimens with ≥85.% Bayesian predictive probability of success (i.e. demonstrating superiority to control) in a future 300-patient phase 3 neoadjuvant trial with a pCR endpoint. This run-in arm was conducted to determine safety of combining tucatinib with paclitaxel/trastuzumab/pertuzumab, monitoring special adverse events of interest including LFT elevations and gastrointestinal toxicities.Methods: The I-SPY 2 methods have been previously published. Results: 20 pts were evaluable in tucatinib treatment arm. The control arm included 329 historical controls enrolled since April 2010. The initial tucatinib dose was 300 mg BID. After enrollment of the first 8 pts, there were 3 pts with grade 3 LFT elevations, 2 pts with grade 2/3 diarrhea, 1 pt with grade 2 neutropenia, and 1 pt with grade 3 nausea. After this safety review, the tucatinib dose was lowered to 250 mg BID. Among 5 additional pts enrolled, 3 developed grade 2/3 LFT abnormalities. The protocol was then modified to tucatinib 150 mg BID days 1-28 and then 250 mg BID days 29-84; 7 pts were treated. Safety data were reviewed after 20 pts were enrolled; the arm was then suspended due to similar LFT elevations regardless of tucatinib dose reduction or schedule. 7 of 20 pts (35%) had reversible Grade 3 or higher ALT/AST elevation (Table). No pt met criteria for Hy’s Law. In terms of efficacy, 12 of 14 evaluable pts had &amp;gt; 80% reduction of tumor volume by 12 weeks, measured by MRI assessment of functional tumor volume (FTV). Conclusion: The goal of the run-in arm was to determine the safety of adding tucatinib to the combination of paclitaxel/trastuzumab/pertuzumab. The addition of tucatinib resulted in unacceptable but reversible LFT elevations despite tucatinib dose reduction. Tucatinib containing therapy resulted in &amp;gt;80% decline in tumor volume at 12 weeks in 86% of pts. Tucatinib showed a high level of activity when combined with paclitaxel/trastuzumab/pertuzumab, but the combination is not feasible. Table: Number of pts with grade 2, 3, and 4 LFT elevations by treatment schedule (highest grade per patient per event, ALT or Treatment scheduleGrade 2 LFT elevationGrade 3 LFT elevationGrade 4 LFT elevationTucatinib 300 mg BID030Tucatinib 250 mg BID210Tucatinib 150 mg BID days 1-28 followed by 250 mg BID days 29 to 84112 Citation Format: David A Potter, Erin Roesch, Christina Yau, Ruixiao Lu, Denise Wolf, Susan Samson, Debra Stafford, Kathy S Albain, Claudine Isaacs, Meghana Trivedi, Douglas Yee, Judy Boughey, Alexandra Thomas, A. Jo Chien, Nola Hylton, Wen Li, Angela DeMichele, Jane Perlmutter, W. Fraser Symmans, Dawn L Hershman, Michelle Melisko, Laura J van 't Veer, Amy Wilson, Smita M Asare, Donald A Berry, Richard Schwab, Hope S Rugo, Laura J Esserman. Evaluation of Tucatinib + (Paclitaxel + Pertuzumab + Trastuzumab) followed by AC in high-risk HER2 positive (HER2+) stage II/III breast cancer: Results from the I-SPY 2 TRIAL [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr PD8-07.

Abstract PD8-05: Overall survival (OS) results from the phase III PHENIX trial of HER2+ metastatic breast cancer treated with pyrotinib plus capecitabine

Abstract Background: Pyrotinib (an irreversible tyrosine kinase inhibitor targeting EGFR, HER2, and HER4) plus capecitabine previously demonstrated a statistically significant improvement in progression-free survival (PFS) over placebo plus capecitabine for HER2-positive local relapsed or metastatic breast cancer after prior trastuzumab and taxanes in the interim analysis of the PHENIX trial (NCT02973737; Jiang Z et al. Oral presentation at ASCO 2019, Abstract 1001). It is shown that patients also benefit from subsequent pyrotinib monotherapy after progressed on capecitabine alone. Here we present an updated OS from a follow-up period with a median of 42.1 months. Methods: This PHENIX trial enrolled patients with HER2-positive local relapsed or metastatic breast cancer who had received prior trastuzumab and taxanes and up to two prior lines of chemotherapy for relapsed or metastatic disease. Eligible patients were randomized 2:1 to receive pyrotinib (400 mg orally once daily) in combination with capecitabine (1000 mg/m2 orally twice daily on days 1-14 for 21-day cycles; P+C group) or placebo plus capecitabine followed by pyrotinib monotherapy upon disease progression (C-P group). Randomization was stratified by the presence of visceral disease (yes vs. no) and the hormone receptor status (estrogen receptor [ER]- and/or progesterone receptor [PR]-positive vs. ER- and PR-negative). The primary endpoint was the independent review committee-assessed PFS. The data cutoff for the updated OS analysis was January 15, 2021. Results: A total of 279 eligible patients were randomized, with 185 to P+C group and 94 to C-P group. As of data cutoff, the median duration of follow-up was 41.7 months (95% CI 40.2-42.4) in P+C group and 43.1 months (95% CI 38.8-44.5) in C-P group. 71 out of 94 patients who progressed on placebo plus capecitabine received pyrotinib monotherapy as the first subsequent anti-cancer therapy according to protocol. Excluding the protocol prespecified pyrotinib monotherapy, 129 (69.7%) patients in the P+C group and 74 (78.7%) patients in the C-P group received anti-cancer therapy after discontinuing study treatment, and 107 (57.8%) patients and 61 (64.9%) patients received post-discontinuation anti-HER2 drugs, respectively. 98 (53.0%) of the 185 patients in P+C group and 59 (62.8%) of the 94 patients in C-P group died by the time of data cutoff. Kaplan-Meier estimated median OS was 34.9 months (95% CI 28.4-42.1) in P+C group and 23.6 months (95% CI 19.3-34.4) in C-P group (HR 0.74, 95% CI 0.54-1.02; p=0.068). The 2-year OS rate was 65.2% (95% CI 57.6%-71.8%) versus 48.9% (95% CI 38.1%-58.7%), respectively. Subgroup analyses of OS were generally consistent with the overall result (Table 1). Conclusion: The updated OS analysis highlighted the long-term efficacy of pyrotinib plus capecitabine in pretreated HER2-positive local relapsed or metastatic breast cancer. We did not observe a statistically significant difference in OS between pyrotinib plus capecitabine group and capecitabine group followed by subsequent pyrotinib monotherapy upon disease progression. Table 1.Subgroup analysis of OS.Pyrotinib plus capecitabine (n=185)Placebo plus capecitabine (n=94)HR (95% CI) *Brain metastasesPresentEvents14/21 (66.7)8/10 (80.0)Median OS22.9 (19.7-35.0)17.3 (1.6-34.4)0.77 (0.32-1.84)AbsentEvents84/164 (51.2)51/84 (60.7)Median OS36.7 (30.7-43.0)23.6 (21.5-40.4)0.72 (0.51-1.02)Previous chemotherapyNoneEvents29/60 (48.3)12/22 (54.5)Median OS37.5 (34.2-NA)32.6 (18.9-NA)0.75 (0.38-1.47)1 lineEvents34/70 (48.6)27/47 (57.4)Median OS35.6 (25.9-NA)31.6 (18.0-NA)0.73 (0.44-1.21)2 linesEvents30/44 (68.2)13/18 (72.2)Median OS21.1 (13.6-33.4)15.9 (5.4-44.0)0.77 (0.40-1.49)Data are n/N (%) or median (95% CI). NA, not available. *HRs are from unstratified analyses. Citation Format: Zefei Jiang, Min Yan, Li Bian, Tao Wang, Xichun Hu, Qingyuan Zhang, Quchang Ouyang, Jifeng Feng, Yongmei Yin, Tao Sun, Zhongsheng Tong, Xiaojia Wang, Herui Yao, Shuping Jiang, Xiaoyu Zhu, Jianjun Zou. Overall survival (OS) results from the phase III PHENIX trial of HER2+ metastatic breast cancer treated with pyrotinib plus capecitabine [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr PD8-05.

Abstract GS3-02: Updated overall survival (OS) results from the phase 3 PHOEBE trial of pyrotinib versus lapatinib in combination with capecitabine in patients with HER2-positive metastatic breast cancer

Abstract Background: Pyrotinib (an irreversible tyrosine kinase inhibitor targeting EGFR, HER2 and HER4) plus capecitabine significantly improved progression-free survival (PFS) compared with that for lapatinib plus capecitabine in women with HER2-positive metastatic breast cancer after treatment with trastuzumab and taxanes in the interim analysis of the PHOEBE trial (NCT03080805; Xu et al. Lancet Oncology, 2021). In this report, we present an updated analysis of the overall survival data from this trial. Methods: This PHOEBE trial enrolled patients with HER2-positive metastatic breast cancer who had received prior trastuzumab and taxanes and up to two prior lines of chemotherapy for metastatic disease. Patients were randomly assigned (1:1) to receive either oral pyrotinib 400 mg or lapatinib 1250 mg once daily, combined with oral capecitabine 1000 mg/m² twice daily on days 1-14 of each 21-day cycle. Stratification factors were hormone receptor status (estrogen receptor [ER]- and/or progesterone receptor [PR]-positive vs. ER- and PR-negative) and previous lines of chemotherapy for metastatic disease (≤1 vs 2). The primary endpoint was PFS assessed by masked independent central review. Data cutoff for the updated overall survival analysis was March 31, 2021. Results: Between July 31, 2017 and October 30, 2018, 267 eligible patients were enrolled and randomized to either pyrotinib plus capecitabine (pyrotinib group) or lapatinib plus capecitabine (lapatinib group). 134 patients in pyrotinib group and 132 in lapatinib group started the assigned treatment. At data cutoff, the median follow-up duration was 33.2 months (95% CI 31.4-34.2) in the pyrotinib group and 31.8 months (95% CI 31.2-34.1) in the lapatinib group. 78 (58.2%) patients in the pyrotinib group and 98 (74.2%) patients in the lapatinib group received post-discontinuation therapy, with trastuzumab (60 [44.8%] in the pyrotinib group and 65 [49.2%] in the lapatinib group) being the most common. As of data cutoff date, 54 (40.3%) of 134 patients randomly assigned to the pyrotinib group and 69 (52.3%) of the 132 patients randomly assigned to lapatinib group had died. Median OS was not reached (95% CI 34.0-not reached) in the pyrotinib group and 26.9 months (22.4-not reached) in the lapatinib group (HR 0.69 [95% CI 0.48-0.98]; P=0.019). Kaplan-Meier estimated OS at 24 months was 66.6% (95% CI 57.7-74.0) and 58.8% (95% CI 49.7-66.7), respectively. 99 (73.9%) patients in the pyrotinib group and 121 (91.7%) in the lapatinib group had disease progression or had died. Pyrotinib plus capecitabine significantly improved PFS assessed by investigator compared with that for lapatinib plus capecitabine (12.5 months [95% CI 9.8-13.8] vs 5.6 months [95% CI 5.5-7.0]; HR 0.48 [95% CI 0.37-0.63]; P&amp;lt;0.0001). The benefits of pyrotinib plus capecitabine were observed in most clinically relevant subgroups for the updated analysis of both OS and PFS (Table 1). Conclusion: With extended follow-up, pyrotinib plus capecitabine demonstrated statistically significant OS improvement compared with lapatinib plus capecitabine in patients with HER2-positive metastatic breast cancer after trastuzumab and chemotherapy. This updated analysis of overall survival in the PHOEBE trial reaffirmed pyrotinib plus capecitabine as an established treatment option in this patient population. Table 1.Subgroup analysis of OS and PFS per investigator.HR for OSHR for PFSAll Patients0.69 (0.48-0.98)0.48 (0.37-0.63)Trastuzumab therapy for metastatic disease&amp;lt;3 months0.67 (0.33-1.35)0.34 (0.17-0.69)3-6 months0.78 (0.34-1.76)0.66 (0.32-1.34)≥3 months0.79 (0.37-1.66)0.44 (0.26-0.75)Trastuzumab resistanceNo0.60 (0.39-0.91)0.44 (0.32-0.61)Yes0.94 (0.48-1.85)0.58 (0.35-0.98)HER2 amplification by FISH0.76 (0.39-1.51)0.57 (0.35-0.92)Pathological gradingII0.65 (0.33-1.28)0.51 (0.31-0.85)III0.82 (0.41-1.65)0.51 (0.31-0.83)Unknown0.70 (0.41-1.21)0.45 (0.29-0.70)Visceral lesionsVisceral0.59 (0.40-0.88)0.45 (0.33-0.62)Non-visceral1.28 (0.55-2.95)0.57 (0.31-1.04)ECOG performance status00.72 (0.40-1.29)0.42 (0.26-0.66)10.67 (0.43-1.04)0.50 (0.36-0.71)Estrogen and progesterone receptor statusPositive0.74 (0.44-1.25)0.58 (0.39-0.86)Negative0.64 (0.39-1.04)0.41 (0.28-0.60)Previous lines of chemotherapy for metastatic disease00.72 (0.38-1.35)0.47 (0.30-0.74)10.73 (0.44-1.22)0.49 (0.32-0.73)20.56 (0.24-1.32)0.56 (0.28-1.08)Data are median (95% CI). HRs are from unstratified analyses. Citation Format: Binghe Xu, Min Yan, Fei Ma, Xichun Hu, Jifeng Feng, Quchang Ouyang, Zhongsheng Tong, Huiping Li, Qingyuan Zhang, Tao Sun, Xian Wang, Yongmei Yin, Ying Cheng, Wei Li, Xiaoyu Zhu, Chunxia Chen, Jianjun Zou. Updated overall survival (OS) results from the phase 3 PHOEBE trial of pyrotinib versus lapatinib in combination with capecitabine in patients with HER2-positive metastatic breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr GS3-02.

Abstract P2-13-32: Pyrotinib in combination with letrozole for estrogen receptor (ER)-positive, human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer: A multicenter, single-arm, phase II trial

Abstract Background: HER2-targeted agents combined with endocrine therapy (ET) has been recommended as an optional therapeutic strategy for hormone receptor (HR)/human epidermal growth factor receptor 2 (HER2) co-positive metastatic breast cancer (MBC). Pyrotinib is an oral irreversible pan-ErbB receptor tyrosine kinase inhibitor targeting EGFR, HER2 and HER4, with proven efficacy in combination with chemotherapy in HER2-positive MBC. This multicenter, single-arm phase 2 trial aimed to investigate the efficacy and safety of pyrotinib plus letrozole in patients with estrogen receptor (ER)-positive, HER2-positive MBC (NCT04407988). Methods: Pre-/perimenopausal or postmenopausal women with histologically confirmed HER2-positive (immunohistochemistry [IHC] 3+ or 2+ with fluorescence in situ hybridization positive) and ER-positive (the percentage of ER+ cells ≥ 10% by IHC) MBC were enrolled. Prior treatment for metastatic disease was not allowed. Eligible patients received pyrotinib (400 mg, po, qd) plus letrozole (2.5 mg, po, qd) until disease progression or unacceptable toxicity. For pre-/perimenopausal patients, additional treatment with ovarian function suppression (OFS) was required. The primary endpoint was clinical benefit rate (CBR), defined as the rate of patients with complete response (CR), partial response (PR), or stable disease (SD) for at least 24 weeks per RECIST 1.1. Secondary endpoints included objective response rate (ORR), progression-free survival (PFS), overall survival (OS), and safety. Results: Between December 3, 2019 and April 2, 2021, 26 patients were enrolled. As of July 5, 2021, CBR was 76.9% (20 of 26; 95% CI 56.4% to 91.0%) and ORR was 57.7% (15 of 26; 95% CI 36.9% to 76.6%). One of the 26 patients (3.8%) had CR, 14 (53.8%) had PR, 5 (19.2%) had SD, 5 (19.2%) had progressive disease, and 1 (3.8%) had not evaluable disease. The benefits in CBR and ORR were observed across all subgroups. The most common any grade AEs were diarrhea (25 of 26, 96.2%), vomiting (8 of 26, 30.8%), nausea (6 of 26, 23.1%), and oral ulceration (6 of 26, 23.1%). Diarrhea was the only reported grade 3 AE that occurred in 5 patients (19.2%). No grade 4 or 5 AEs occurred during this study. Conclusions: Pyrotinib combined with letrozole showed an encouraging antitumor activity with good tolerance in patients with ER/HER2 co-positive MBC, promising as an alternative treatment option for this disease. The study is ongoing. Citation Format: Quchang Ouyang, Huihua Xiong, Min Yan, Jincai Zhong, Li Ran, Ting Luo, Liping Liu, Jing Li, Xiaohong Yang, Huawu Xiao, Ning Xie, Hui Wu, Jianxiang Gao, Jun Lu, Xuming Hu, Zheyu Hu, Can Tian, Zhengrong Shui, Min Cao. Pyrotinib in combination with letrozole for estrogen receptor (ER)-positive, human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer: A multicenter, single-arm, phase II trial [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P2-13-32.

Abstract P2-13-31: Pyrotinib in combination with docetaxel as first-line treatment for HER2-positive metastatic breast cancer (PANDORA): A single-arm, multicenter phase 2 trial

Abstract Background: Human epidermal growth factor receptor 2 (HER2) targeted therapy in combination with chemotherapy is the recommended first-line strategy for HER2-positive metastatic breast cancer. Pyrotinib is a small molecule tyrosine kinase inhibitor targeting HER1, HER2, and HER4. The phase 3 PHOEBE trial has proved its superiority over lapatinib when in combination with capecitabine in previously treated, HER2-positive metastatic breast cancer. This phase 2 trial aimed to investigate the activity of pyrotinib plus docetaxel as first-line treatment in HER2-positive metastatic breast cancer. Methods: Patients with measurable disease received oral pyrotinib 400 mg once daily until disease progression or intolerable toxicity. Intravenous docetaxel was given at 75 mg/m2 on day 1 for at least six 21-day cycles. The primary endpoint was investigator-assessed objective response rate (ORR) per RECIST 1.1. As per Simon’s optimal two-stage design, if 18 or more of 27 patients achieved complete response (CR) or partial response (PR) in the first stage, additional 40 patients would be enrolled. If 47 or more of 67 patients achieved CR or PR, the study was deemed successful. Considering a dropout rate of 15%, 79 patients were needed. The study is registered with ClinicalTrials.gov, NCT03876587. Results: Between June 2019 and June 2021, a total of 79 patients enrolled and received study treatment. As of June 18, 2021, 14 patients had not undergone response evaluation or had unconfirmed response, while 65 patients were included in the full analysis set. There were two patients meeting the exclusion criteria, leaving 63 patients in the per-protocol set. Of 65 patients, the median age was 52 years (range, 28-70). Most of them had Eastern Cooperative Oncology Group performance status of 1 (69.2%), visceral metastases (56.9%), hormone receptor-positive disease (55.4%), and prior (neo)adjuvant therapy with (27.7%) or without trastuzumab (32.3%). In the first stage, 24 of 27 patients achieved confirmed objective response (one CR and 23 PR), and the study proceeded to the second stage. The confirmed ORR in 65 patients was 78.5% (95% CI, 66.5%-87.7%); two patients achieved CR and 49 achieved PR. The confirmed ORR in the per-protocol set (n=63) was 81.0% (95% CI, 69.1%-89.8%). Progression-free survival was immature. Of 65 patients, the most common grade ≥3 treatment-emergent. adverse events included decreased neutrophil count (30.8%), decreased white blood cell count (26.2%), diarrhea (20.0%), and hypokalemia (6.2%). Grade ≥3 diarrhea was less common in patients with loperamide prophylaxis (5.3%; 2/38) than in those without loperamide prophylaxis (40.7%; 11/27). Conclusions: Pyrotinib in combination with docetaxel exhibits promising antitumor activity and acceptable safety profile among patients with HER2-positive metastatic breast cancer in the first-line setting. Loperamide prophylaxis is an effective approach for the prevention of diarrhea. Citation Format: Xiaojia Wang, Jian Huang, Yabing Zheng, Xiying Shao, Wenming Cao, Zhanhong Chen, Yanxia Shi, Li Cai, Wenyan Chen, Zhen Guo, Jian Liu, Peng Shen, Yiding Chen, Xian Wang, Huiping Li, Man Li. Pyrotinib in combination with docetaxel as first-line treatment for HER2-positive metastatic breast cancer (PANDORA): A single-arm, multicenter phase 2 trial [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P2-13-31.