Preclinical and clinical development of afatinib: a focus on breast cancer and squamous cell carcinoma of the head and neck

Antibody-assisted target identification reveals afatinib, an EGFR covalent inhibitor, down-regulating ribonucleotide reductase

Afatinib, used for the first-line treatment of non-small-cell lung carcinoma (NSCLC) patients with distinct epidermal growth factor receptor (EGFR) mutations, inactivates EGFR by mimicking ATP structure and forming a covalent adduct with EGFR. We developed a method to unravel potential targets of afatinib in NSCLC cells through immunoprecipitation of afatinib-labeling proteins with anti-afatinib antiserum and mass spectrometry analysis. Ribonucleotide reductase (RNR) is one of target proteins of afatinib revealed by this method. Treatment of afatinib at 10-100 nM potently inhibited intracellular RNR activity in an in vitro assay using permeabilized PC-9 cells (formerly known as PC-14). PC-9 cells treated with 10 μM afatinib displayed elevated markers of DNA damage. Long-term treatment of therapeutic concentrations of afatinib in PC-9 cells caused significant decrease in protein levels of RNR subunit M2 at 1-10 nM and RNR subunit M1 at 100 nM. EGFR-null Chinese hamster ovary (CHO) cells treated with afatinib also showed similar effects. Afatinib repressed the upregulation of RNR subunit M2 induced by gemcitabine. Covalent modification with afatinib resulting in inhibition and protein downregulation of RNR underscores the therapeutic and off-target effects of afatinib. Afatinib may serve as a lead compound of chemotherapeutic drugs targeting RNR. This method can be widely used in the identification of potential targets of other covalent drugs.

Novel multi-targeted ErbB family inhibitor afatinib blocks EGF-induced signaling and induces apoptosis in neuroblastoma

Neuroblastoma is the most common extracranial solid tumor in children. The ErbB family of proteins is a group of receptor tyrosine kinases that promote the progression of various malignant cancers including neuroblastoma. Thus, targeting them with small molecule inhibitors is a promising strategy for neuroblastoma therapy. In this study, we investigated the anti-tumor effect of afatinib, an irreversible inhibitor of members of the ErbB family, on neuroblastoma. We found that afatinib suppressed the proliferation and colony formation ability of neuroblastoma cell lines in a dose-dependent manner. Afatinib also induced apoptosis and blocked EGF-induced activation of PI3K/AKT/mTOR signaling in all neuroblastoma cell lines tested. In addition, afatinib enhanced doxorubicin-induced cytotoxicity in neuroblastoma cells, including the chemoresistant LA-N-6 cell line. Finally, afatinib exhibited antitumor efficacy in vivo by inducing apoptosis in an orthotopic xenograft neuroblastoma mouse model. Taken together, these results show that afatinib inhibits neuroblastoma growth both in vitro and in vivo by suppressing EGFR-mediated PI3K/AKT/mTOR signaling. Our study supports the idea that EGFR is a potential therapeutic target in neuroblastoma. And targeting ErbB family protein kinases with small molecule inhibitors like afatinib alone or in combination with doxorubicin is a viable option for treating neuroblastoma.

Breast cancer resistance protein (BCRP/ABCG2) and P-glycoprotein (P-gp/ABCB1) transport afatinib and restrict its oral availability and brain accumulation

Afatinib is a highly selective, irreversible inhibitor of EGFR and HER-2. It is orally administered for the treatment of patients with EGFR mutation-positive types of metastatic NSCLC. We investigated whether afatinib is a substrate for the multidrug efflux transporters ABCB1 and ABCG2 and whether these transporters influence oral availability and brain and other tissue accumulation of afatinib. We used in vitro transport assays to assess human (h)ABCB1-, hABCG2- or murine (m)Abcg2-mediated transport of afatinib. To study the single and combined roles of Abcg2 and Abcb1a/1b in oral afatinib disposition, we used appropriate knockout mouse strains. Afatinib was transported well by hABCB1, hABCG2 and mAbcg2 in vitro. Upon oral administration of afatinib, Abcg2^-/-, Abcb1a/1b^-/- and Abcb1a/1b^-/-;Abcg2^-/- mice displayed a 4.2-, 2.4- and 7-fold increased afatinib plasma AUC_0-24 compared with wild-type mice. Abcg2-deficient strains also displayed decreased afatinib plasma clearance. At 2h, relative brain accumulation of afatinib was not significantly altered in the single knockout strains, but 23.8-fold increased in Abcb1a/1b^-/-;Abcg2^-/- mice compared to wild-type mice. Abcg2 and Abcb1a/1b restrict oral availability and brain accumulation of afatinib. Inhibition of these transporters may therefore be of clinical importance for patients with brain (micro)metastases positioned behind an intact blood-brain barrier.

Effects of neratinib and combination with irradiation and chemotherapy in head and neck cancer cells

OBJECTIVE

Prognosis of patients with head and neck squamous cell carcinoma (HNSCC) is still poor. Novel therapeutic approaches are of great interest to improve the effects of radiochemotherapy. We evaluated the effects of tyrosine kinase inhibitor neratinib on HNSCC cell lines CAL27, SCC25 and FaDu as a single agent and in combination with irradiation and chemotherapy.

METHODS

Effects of neratinib were evaluated in HNSCC cell lines CAL27, SCC25 and FaDu. Effect on cell viability of neratinib and combination with cisplatin and irradiation was measured using CCK-8 assays and clonogenic assays. Western blot analysis was performed to distinguish the effect on epithelial growth factor receptor and HER2 expression. Apoptosis was evaluated by flow cytometry analysis.

RESULTS

Growth inhibition was achieved in all cell lines, whereas combination of cisplatin and neratinib showed greater inhibition than each agent alone. Apoptosis was induced in all cell lines. Combination of neratinib with irradiation or cisplatin showed significantly increased apoptosis. In clonogenic assays, significant growth inhibition was observed in all investigated cell lines.

CONCLUSION

Neratinib, as a single agent or in combination with chemo-irradiation, may be a promising treatment option for patients with head and neck cancer.

Inhibition of proliferation and induction of apoptosis in RB116 retinoblastoma cells by afatinib treatment

The present study investigates the effect of afatinib on the growth, induction of apoptosis in RB116 cells, and reduction of carcinoma growth in the mice transplanted with RB116 cells. The results from MTT assay revealed that afatinib inhibited the growth of RB116 cells in a dose-dependent manner. Proliferation of RB116 cells was reduced to 64 % on treatment with 200 μM concentration of afatinib after 48 h. Afatinib treatment of RB116 cells at 200 μM concentration induced apoptosis and necrosis in 49.7 and 9.4 %, respectively, after 48 h. In the RB116-transplanted mice, treatment with afatinib at 10-mg/kg doses for 45 days caused a significant (p < 0.005) reduction in the tumor volume compared to the control group. The tissue lysates of the mice containing RB116 transplant showed a significant decrease in the expressions of Ki67 and p53 in the afatinib treatment group after 45 days. However, the expression of caspase-3 was increased and of Bcl-2 remained unaltered on treatment with afatinib. Measurement of the body weight of afatinib-treated animals showed no reduction during the study. Thus, afatinib can be of therapeutic value for the treatment of retinoblastoma.

Afatinib inhibits proliferation and invasion and promotes apoptosis of the T24 bladder cancer cell line

Afatinib is a highly selective, irreversible inhibitor of the epidermal growth factor receptor (EGFR) and human EGFR 2 (HER-2). Although preclinical and clinical studies have indicated that afatinib has antitumor activity and clinical efficacy in non-small cell lung carcinoma, head and neck squamous cell carcinoma and breast cancer, there are few studies investigating its inhibitory effect on human bladder carcinoma cells. In this study, the antitumor effect of afatinib was investigated on the T24 bladder cancer cell line. The T24 bladder cancer cell line was treated with afatinib at various concentrations (0, 1, 5, 10 and 20 µmol/l). MTT assay was used to estimate the proliferation of the T24 cells; flow cytometric analysis was used to estimate the effect of afatinib on T24 cell apoptosis; cell invasion ability was assessed by a Transwell invasion assay; and western blot analysis was used to detect the expression of Bcl-2, Bax, Akt, extracellular-signal-regulated kinase (ERK)1/2, matrix metalloproteinase (MMP)-2 and MMP-9. The MTT assay demonstrated that afatinib inhibited the proliferation of T24 cells in a dose- and time-dependent manner. Flow cytometric analysis revealed that the cell apoptosis rate increased as the concentration of afatinib increased. The cell invasion assay indicated that afatinib treatment significantly inhibited the invasive behavior of T24 cells in a dose-dependent manner. Western blot analysis showed that with increasing afatinib concentrations, Bcl-2, phosphorylated (p)-ERK1/2, p-Akt, MMP-2 and MMP-9 expression levels were significantly decreased, whereas total (t)-ERK1/2 and t-Akt expression levels remained basically unchanged, and Bax expression levels were greatly increased. The results indicate that afatinib inhibits the proliferation and invasion of T24 cells in vitro and induces the apoptosis of these cells by inhibiting the EGFR signaling network.

HER2 as a therapeutic target in head and neck squamous cell carcinoma

The majority of patients with head and neck squamous cell carcinoma (HNSCC) present with advanced-stage disease. The current standard of care is surgery followed by adjuvant radiotherapy with or without chemotherapy or chemoradiation alone. The addition of cetuximab for the treatment of patients with locally advanced or recurrent/metastatic HNSCC has improved overall survival and locoregional control; however, responses are often modest, and treatment resistance is common. A variety of therapeutic strategies are being explored to overcome cetuximab resistance by blocking candidate proteins implicated in resistance mechanisms such as HER2. Several HER2 inhibitors are in clinical development for HNSCC, and HER2-targeted therapy has been approved for several cancers. This review focuses on the biology of HER2, its role in cancer development, and the rationale for clinical investigation of HER2 targeting in HNSCC.

A neoadjuvant, randomized, open-label phase II trial of afatinib versus trastuzumab versus lapatinib in patients with locally advanced HER2-positive breast cancer

BACKGROUND

Chemotherapy is standard neoadjuvant treatment of LA BC. Patients with HER2-positive BC require targeted therapy. Trastuzumab and pertuzumab, which target HER2, with chemotherapy are approved as neoadjuvant therapy, however, treatments with different mechanisms of action might provide a broader range of activity. In this study we evaluated the efficacy and safety of the irreversible ErbB family blocker afatinib, versus trastuzumab or lapatinib in the neoadjuvant treatment of HER2-positive, LA BC.

PATIENTS AND METHODS

Treatment-naive, HER2-positive BC patients with stage IIIA, B, C or inflammatory disease were randomized 1:1:1 to daily afatinib (50 mg), lapatinib (1500 mg), or weekly trastuzumab (4 mg/kg loading dose, then 2 mg/kg/wk) for 6 weeks until surgery or follow-up neoadjuvant treatment. The primary end point was objective response rate according to Response Evaluation Criteria in Solid Tumors (version 1.0).

RESULTS

Recruitment was stopped early because of slow patient enrollment; 29 patients were randomized to afatinib (n = 10), lapatinib (n = 8), or trastuzumab (n = 11). Objective response was seen in 8 afatinib-, 6 lapatinib-, and 4 trastuzumab-treated patients. Eleven patients had stable disease (best response); 1 lapatinib- and 1 trastuzumab-treated patient had progressive disease. All 10 afatinib-treated patients experienced drug-related adverse events (commonly diarrhea, dermatitis acneiform, and paronychia) versus 6 of 8 lapatinib- (diarrhea and rash) and 5 of 11 trastuzumab-treated patients (vomiting and arthralgia).

CONCLUSION

Afatinib demonstrated clinical activity that compared favorably to trastuzumab and lapatinib for neoadjuvant treatment of HER2-positive BC, with a safety profile consistent with epidermal growth factor receptor tyrosine kinase inhibitors.

A comprehensive review of the preclinical efficacy profile of the ErbB family blocker afatinib in cancer

Afatinib (also known as BIBW 2992) has recently been approved in several countries for the treatment of a distinct type of epidermal growth factor receptor (EGFR)-mutated non-small cell lung cancer. This manuscript comprehensively reviews the preclinical data on afatinib, an irreversible inhibitor of the tyrosine kinase activity of members of the epidermal growth factor receptor family (ErbB) including EGFR, HER2 and ErbB4. Afatinib covalently binds to cysteine 797 of the EGFR and the corresponding cysteines 805 and 803 in HER2 and ErbB4, respectively. Such covalent binding irreversibly inhibits the tyrosine kinase activity of these receptors, resulting in reduced auto- and transphosphorylation within the ErbB dimers and inhibition of important steps in the signal transduction of all ErbB receptor family members. Afatinib inhibits cellular growth and induces apoptosis in a wide range of cells representative for non-small cell lung cancer, breast cancer, pancreatic cancer, colorectal cancer, head and neck squamous cell cancer and several other cancer types exhibiting abnormalities of the ErbB network. This translates into tumour shrinkage in a variety of in vivo rodent models of such cancers. Afatinib retains inhibitory effects on signal transduction and in vitro and in vivo cancer cell growth in tumours resistant to reversible EGFR inhibitors, such as those exhibiting the T790M mutations. Several combination treatments have been explored to prevent and/or overcome development of resistance to afatinib, the most promising being those with EGFR- or HER2-targeted antibodies, other tyrosine kinase inhibitors or inhibitors of downstream signalling molecules.