Delong Liu

Third-generation inhibitors targeting EGFR T790M mutation in advanced non-small cell lung cancer.

The tyrosine kinase inhibitors (TKI) against epidermal growth factor receptor (EGFR) are widely used in patients with non-small cell lung cancer (NSCLC). However, EGFR T790M mutation leads to resistance to most clinically available EGFR TKIs. Third-generation EGFR TKIs against the T790M mutation have been in active clinical development. These agents include osimertinib, rociletinib, HM61713, ASP8273, EGF816, and PF-06747775. Osimertinib and rociletinib have shown clinical efficacy in phase I/II trials in patients who had acquired resistance to first- or second-generation TKIs. Osimertinib (AZD9291, TAGRISSO) was recently approved by FDA for metastatic EGFR T790M mutation-positive NSCLC. HM61713, ASP8237, EGF816, and PF-06747775 are still in early clinical development. This article reviews the emerging data regarding third-generation agents against EGFR T790M mutation in the treatment of patients with advanced NSCLC.

ABT-199 (venetoclax) and BCL-2 inhibitors in clinical development

With the advent of new agents targeting CD20, Bruton’s tyrosine kinase, and phosphoinositol-3 kinase for chronic lymphoid leukemia (CLL), more treatment options exist than ever before. B-cell lymphoma-2 (BCL-2) plays a major role in cellular apoptosis and is a druggable target. Small molecule inhibitors of BCL-2 are in active clinical studies. ABT-199 (venetoclax, RG7601, GDC-0199) has been granted breakthrough designation by FDA for relapsed or refractory CLL with 17p deletion. In this review, we summarized the latest clinical development of ABT-199/venetoclax and other novel agents targeting the BCL-2 proteins.

Novel ALK inhibitors in clinical use and development

Anaplastic lymphoma kinase 1 (ALK-1) is a member of the insulin receptor tyrosine kinase family. ALK-1 was initially found in anaplastic large cell lymphoma (ALCL). ALK mutations have also been implicated in the pathogenesis of non-small cell lung cancer (NSCLC) and other solid tumors. Multiple small molecule inhibitors with activity against ALK and related oncoproteins are under clinical development. Two of them, crizotinib and ceritinib, have been approved by FDA for treatment of locally advanced and metastatic NSCLC. More agents (alectinib, ASP3026, X396) with improved safety, selectivity, and potency are in the pipeline. Dual inhibitors targeting ALK and EGFRm (AP26113), TRK (TSR011), FAK (CEP-37440), or ROS1 (RXDX-101, PF-06463922) are under active clinical development.

Acalabrutinib (ACP-196): a selective second-generation BTK inhibitor

More and more targeted agents become available for B cell malignancies with increasing precision and potency. The first-in-class Bruton’s tyrosine kinase (BTK) inhibitor, ibrutinib, has been in clinical use for the treatment of chronic lymphocytic leukemia, mantle cell lymphoma, and Waldenstrom’s macroglobulinemia. More selective BTK inhibitors (ACP-196, ONO/GS-4059, BGB-3111, CC-292) are being explored. Acalabrutinib (ACP-196) is a novel irreversible second-generation BTK inhibitor that was shown to be more potent and selective than ibrutinib. This review summarized the preclinical research and clinical data of acalabrutinib.

Second- and third-generation ALK inhibitors for non-small cell lung cancer

Crizotinib as the first-generation ALK inhibitor has shown significant activity in ALK-mutated non-small cell lung cancer (NSCLC). Second- and third-generation ALK inhibitors are entering clinical applications for ALK+ NSCLC. In addition, a third-generation ALK inhibitor, lorlatinib (PF-06463922), was reported to resensitize NSCLC to crizotinib. This review provided a summary of clinical development of alectinib, ceritinib, brigatinib (AP26113), and lorlatinib.

Selective inhibitors of nuclear export (SINE)- a novel class of anti-cancer agents

Dysregulation of the nucleo-cytoplasmic transport of proteins plays an important role in carcinogenesis. The nuclear export of proteins depends on the activity of transport proteins, exportins. Exportins belong to the karyopherin β superfamily. Exportin-1 (XPO1), also known as chromosomal region maintenance 1 (CRM1), mediates transport of around 220 proteins. In this review, we summarized the development of a new class of antitumor drugs, collectively known as selective inhibitors of nuclear export (SINE). KPT-330 (selinexor) as an oral agent is showing activities in early clinical trials in both solid tumors and hematological malignancies.

Second-generation inhibitors of Bruton tyrosine kinase

Bruton tyrosine kinase (BTK) is a critical effector molecule for B cell development and plays a major role in lymphoma genesis. Ibrutinib is the first-generation BTK inhibitor. Ibrutinib has off-target effects on EGFR, ITK, and Tec family kinases, which explains the untoward effects of ibrutinib. Resistance to ibrutinib was also reported. The C481S mutation in the BTK kinase domain was reported to be a major mechanism of resistance to ibrutinib. This review summarizes the clinical development of novel BTK inhibitors, ACP-196 (acalabrutinib), ONO/GS-4059, and BGB-3111.

EGFR C797S mutation mediates resistance to third-generation inhibitors in T790M-positive non-small cell lung cancer

T790M mutation is the most common mechanism for resistance to first- and second-generation tyrosine kinase inhibitors (TKI) for epidermal growth factor receptor (EGFR). Several third-generation EGFR mutant selective TKIs are being explored to conquer this resistance. AZD9291 (osimertinib, tagrisso) has been approved for treatment of the metastatic EGFR T790M mutation-positive non-small cell lung cancer. Resistance to AZD9291 has been described. C797S mutation was reported to be a major mechanism for resistance to T790M-targeting EGFR inhibitors. This review summarizes the latest development in identifying the C797S mutation and EAI045, the novel selective inhibitor overcoming the C797S mutant.

EAI045: The fourth-generation EGFR inhibitor overcoming T790M and C797S resistance

The third-generation tyrosine kinase inhibitors (TKI), AZD9291 (osimertinib) and CO-1686 (rociletinib) of epidermal growth factor receptor (EGFR) are highly active against T790M positive non-small cell lung cancer (NSCLC). However, resistance develops rapidly. EGFR C797S mutation was reported to be a leading mechanism of resistance to the third-generation inhibitors. The C797S mutation appears to be an ideal target for overcoming the acquired resistance to the third-generation inhibitors. This review summarizes the latest development on the discovery of a fourth-generation EGFR TKI, EAI045.3.

Mechanisms of resistance to third-generation EGFR tyrosine kinase inhibitors.

The tyrosine kinase inhibitors (TKI) of the epidermal growth factor receptor (EGFR) are becoming the first line of therapy for advanced non-small cell lung cancer (NSCLC). Acquired mutations in EGFR account for one of the major mechanisms of resistance to the TKIs. Three generations of EGFR TKIs have been used in clinical applications. AZD9291 (osimertinib; Tagrisso) is the first and only FDA approved third-generation EGFR TKI for T790M-positive advanced NSCLC patients. However, resistance to AZD9291 arises after 9–13 months of therapy. The mechanisms of resistance to third-generation inhibitors reported to date include the EGFR C797S mutation, EGFR L718Q mutation, and amplifications of HER-2, MET, or ERBB2. To overcome the acquired resistance to AZD9291, EAI045 was discovered and recently reported to be an allosteric EGFR inhibitor that overcomes T790M- and C797S-mediated resistance. This review summarizes recent investigations on the mechanisms of resistance to the EGFR TKIs, as well as the latest development of EAI045 as a fourth-generation EGFR inhibitor.