ALK inhibitors are anti-cancer drugs that act on tumours with variations of anaplastic lymphoma kinase (ALK) such as an EML4-ALK translocation. [1] They fall under the category of tyrosine kinase inhibitors, which work by inhibiting proteins involved in the abnormal growth of tumour cells. All the current approved ALK inhibitors function by binding to the ATP pocket of the abnormal ALK protein, blocking its access to energy and deactivating it. A majority of ALK-rearranged NSCLC harbour the EML4-ALK fusion, [2] although as of 2020, over 92 fusion partners have been discovered in ALK+ NSCLC. [3] For each fusion partner, there can be several fusion variants depending on the position the two genes were fused at, and this may have implications on the response of the tumour and prognosis of the patient. [4]
Crizotinib (also a ROS1 and c-MET inhibitor) was approved in Aug 2011 by the US FDA for ALK-positive NSCLC. [5] At the time of the discovery of ALK translocations as a molecular driver in NSCLC, crizotinib was being investigated by Pfizer as a potential c-MET inhibitor. Its activity against ALK being known, Pfizer shifted its investigations to focus on this indication, and obtained a full approval 4 years later. Crizotinib's efficacy was proven in phase III trial, PROFILE 1007, [6] when it was compared to then-standard second-line pemetrexed or docetaxel chemotherapy. [7] [8] [9] It induced tumour stabilisation or shrinkage in 90% of patients. Its lack of penetrance in the brain and non-optimal specificity for ALK meant resistance mostly arose within a year, with the brain being a common site of progression. Blockade of ALKAL2 with crizotinib has been shown to produce analgesic effects in animal models. [10]
Despite the excitement of crizotinib's therapeutic success, there was a need to conceive new drugs with better brain penetrance, higher specificity and targeting a broader set of resistance mutations. As such, Novartis' ceritinib was approved by the FDA in April 2014 for treatment of NSCLC. [2] [11] It provided good brain penetrance and a significant progression-free survival benefit against chemotherapy in the first line as demonstrated in the ASCEND-4 trial. [12]
Roche's alectinib was FDA approved Dec 2015 (accelerated) for patients who had progressed on crizotinib, with full approval in 2017 as a first-line treatment for ALK-positive NSCLC. Like ceritinib, it provided excellent brain penetrance and high response rates. It demonstrated a clear benefit against both first-line chemotherapy and first-line crizotinib. [13] This was based on the phase 3 ALEX trial comparing it with crizotinib. [13]
Ariad's and Takeda's brigatinib (also an inhibitor of mutated EGFR) was the latest second-generation inhibitor and was approved in April 2017 by the US FDA for ALK-positive NSCLC. [14] It is very similar to alectinib in efficacy, while being active against some resistant mutations such as the common G1202R mutation that provides resistance to alectinib.
Pfizer's lorlatinib was the first third-generation inhibitor and was approved in 2018 by the US FDA for ALK-positive NSCLC after progression on a first or second-generation inhibitor. Its macrocyclic structure was designed specifically to address some of the most recalcitrant resistance mutations. Still, most tumours eventually develop resistance through various mechanisms, namely compound-mutations (two or three mutations simultaneously) or activation of alternative pathways, such as the c-MET pathway.
Additional ALK inhibitors currently (or soon to be) undergoing clinical trials include:
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While the response to ALK inhibitors is often very encouraging in patients with ALK+ NSCLC and lasts for a relatively long time, most of them eventually develop resistance, either through mutations in the ATP binding pocket or activation of alternative oncogenic pathways. Much research is being carried out on understanding the ways the cancer adapts and on how to reverse or delay resistance.
The MEK pathway (short for MAPK/ERK-Kinase) has been extensively shown to be critical for the survival of tumour cells subjected to ALK inhibition. [15] Inhibition of this pathway was shown to enhance response and delay the onset of resistance in preclinical models. As of 2020, three clinical trials are running to test the following combinations of ALK inhibitors with MEK inhibitors: brigatinib+binimetinib, [16] ceritinib+trametinib, [17] and alectinib+cobimetinib. [18] Results for the last two are expected around 2020-2021.
The EGFR and HER2 pathways are commonly abnormally activated in a large proportion of cancers. This was shown to be the case in preclinical models of ALK+ NSCLC subjected to ALK inhibition, both in vitro and in vivo. Surprisingly, cells were only sensitive to EGFR/HER2 inhibition when in the process of adapting to ALK inhibitors: both naïve cells and fully-adapted cells showed no measurable response to EGFR/HER2 inhibition alone. [19] Currently, solid preclinical studies have been carried out with second-generation inhibitors combined with afatinib, erlotinib [20] and lapatinib. In all cases, the responses were enhanced by the combination with respect to monotherapy, but seemed more pronounced in afatinib and lapatinib (dual EGFR/HER2 inhibitors) than in erlotinib (which only inhibits EGFR).
Several trials are investigating the combination of anti-VEGF antibody bevacizumab with ALK inhibitors such as alectinib and brigatinib. [21] [22] [23] Bevacizumab is an antiangiogenic antibody, which normalizes the complex blood vessel structures around cancer and prevents new blood vessels from forming, thus starving the tumour and preventing its proliferation.
The use of either radiotherapy or surgery in addition to an ALK inhibitor is known as local consolidation therapy, and as of 2020, it is being investigated by three clinical trials. Their goal is to determine whether it delays resistance to the drugs compared with monotherapy. [24] Some make use of SBRT (stereotactic body radiation therapy), a very precise radiation technique able to provide high doses with minimal side effects. Most trials of LCT in NSCLC focus on oligometastatic disease (under 3-5 lesions, depending on the definitions), but preliminary results of the BRIGHTSTAR trial [24] indicate this method may be safe and well tolerated irrespective of the number of lesions.
NPM-ALK is a different variation/fusion of ALK that drives anaplastic large-cell lymphomas (ALCLs) and is the target of other ALK inhibitors such as TAE-684. [25] [26]
Gefitinib, sold under the brand name Iressa, is a medication used for certain breast, lung and other cancers. Gefitinib is an EGFR inhibitor, like erlotinib, which interrupts signaling through the epidermal growth factor receptor (EGFR) in target cells. Therefore, it is only effective in cancers with mutated and overactive EGFR, but resistances to gefitinib can arise through other mutations. It is marketed by AstraZeneca and Teva.
Non-small-cell lung cancer (NSCLC), or non-small-cell lung carcinoma, is any type of epithelial lung cancer other than small-cell lung cancer (SCLC). NSCLC accounts for about 85% of all lung cancers. As a class, NSCLCs are relatively insensitive to chemotherapy, compared to small-cell carcinoma. When possible, they are primarily treated by surgical resection with curative intent, although chemotherapy has been used increasingly both preoperatively and postoperatively.
Anaplastic lymphoma kinase (ALK) also known as ALK tyrosine kinase receptor or CD246 is an enzyme that in humans is encoded by the ALK gene.
Proto-oncogene tyrosine-protein kinase ROS is an enzyme that in humans is encoded by the ROS1 gene.
Afatinib, sold under the brand name Gilotrif among others, is a medication which is used to treat non-small cell lung carcinoma (NSCLC). It belongs to the tyrosine kinase inhibitor family of medications. It is taken by mouth.
ARIAD Pharmaceuticals, Inc. was an American oncology company, now part of Takeda Oncology, which was founded in 1991 by Harvey J. Berger, M.D. and headquartered in Cambridge, Massachusetts. ARIAD engaged in the discovery, development, and commercialization of medicines for cancer patients.
Treatment of lung cancer refers to the use of medical therapies, such as surgery, radiation, chemotherapy, immunotherapy, percutaneous ablation, and palliative care, alone or in combination, in an attempt to cure or lessen the adverse impact of malignant neoplasms originating in lung tissue.
Targeted therapy of lung cancer refers to using agents specifically designed to selectively target molecular pathways responsible for, or that substantially drive, the malignant phenotype of lung cancer cells, and as a consequence of this (relative) selectivity, cause fewer toxic effects on normal cells.
Adenocarcinoma of the lung is the most common type of lung cancer, and like other forms of lung cancer, it is characterized by distinct cellular and molecular features. It is classified as one of several non-small cell lung cancers (NSCLC), to distinguish it from small cell lung cancer which has a different behavior and prognosis. Lung adenocarcinoma is further classified into several subtypes and variants. The signs and symptoms of this specific type of lung cancer are similar to other forms of lung cancer, and patients most commonly complain of persistent cough and shortness of breath.
Crizotinib, sold under the brand name Xalkori among others, is an anti-cancer medication used for the treatment of non-small cell lung carcinoma (NSCLC). It acts as an ALK and ROS1 inhibitor.
ALK positive lung cancer is a primary malignant lung tumor whose cells contain a characteristic abnormal configuration of DNA wherein, most frequently, the echinoderm microtubule-associated protein-like 4 (EML4) gene is fused to the anaplastic lymphoma kinase (ALK) gene. Less frequently, there will be novel translocation partners for the ALK gene, in place of EML4. This abnormal gene fusion leads to the production of a protein that appears, in many cases, to promote and maintain the malignant behavior of the cancer cells.
Brigatinib, sold under the brand name Alunbrig among others, is a small-molecule targeted cancer therapy being developed by Ariad Pharmaceuticals, Inc. Brigatinib acts as both an anaplastic lymphoma kinase (ALK) and epidermal growth factor receptor (EGFR) inhibitor.
Targeted molecular therapy for neuroblastoma involves treatment aimed at molecular targets that have a unique expression in this form of cancer. Neuroblastoma, the second most common pediatric malignant tumor, often involves treatment through intensive chemotherapy. A number of molecular targets have been identified for the treatment of high-risk forms of this disease. Aiming treatment in this way provides a more selective way to treat the disease, decreasing the risk for toxicities that are associated with the typical treatment regimen. Treatment using these targets can supplement or replace some of the intensive chemotherapy that is used for neuroblastoma. These molecular targets of this disease include GD2, ALK, and CD133. GD2 is a target of immunotherapy, and is the most fully developed of these treatment methods, but is also associated with toxicities. ALK has more recently been discovered, and drugs in development for this target are proving to be successful in neuroblastoma treatment. The role of CD133 in neuroblastoma has also been more recently discovered and is an effective target for treatment of this disease.
Ceritinib is a prescription-only drug used for the treatment of non-small cell lung cancer (NSCLC). It was developed by Novartis and received FDA approval for use in April 2014..Ceritinib is also sold under the brand name Spexib in few countries by Novartis.
Atezolizumab, sold under the brand name Tecentriq, is a monoclonal antibody medication used to treat urothelial carcinoma, non-small cell lung cancer (NSCLC), small cell lung cancer (SCLC), hepatocellular carcinoma and alveolar soft part sarcoma, but discontinued for use in triple-negative breast cancer (TNBC). It is a fully humanized, engineered monoclonal antibody of IgG1 isotype against the protein programmed cell death-ligand 1 (PD-L1).
Alectinib (INN,), sold under the brand name Alecensa, is an anticancer medication that is used to treat non-small-cell lung cancer (NSCLC). It blocks the activity of anaplastic lymphoma kinase (ALK). It is taken by mouth. It was developed by Chugai Pharmaceutical Co. Japan, which is part of the Hoffmann-La Roche group.
Entrectinib, sold under the brand name Rozlytrek, is an anti-cancer medication used to treat ROS1-positive non-small cell lung cancer and NTRK fusion-positive solid tumors. It is a selective tyrosine kinase inhibitor (TKI), of the tropomyosin receptor kinases (TRK) A, B and C, C-ros oncogene 1 (ROS1) and anaplastic lymphoma kinase (ALK).
Lorlatinib, sold under the brand name Lorbrena in the United States, Canada, and Japan, and Lorviqua in the European Union, is an anti-cancer drug developed by Pfizer. It is an orally administered inhibitor of ALK and ROS1, two enzymes that play a role in the development of cancer.
Christine M. Lovly is an associate professor of medicine at Vanderbilt University. Her research involves the development of novel treatment strategies for ALK positive lung cancer.
Repotrectinib, sold under the brand name Augtyro, is an anti-cancer medication used for the treatment of non-small cell lung cancer. It is taken by mouth. Repotrectinib is an inhibitor of proto-oncogene tyrosine-protein kinase ROS1 (ROS1) and of the tropomyosin receptor tyrosine kinases (TRKs) TRKA, TRKB, and TRKC.