Two recent studies suggest alternatives to using FISH assays to test for ALK mutations in non-small-cell lung cancer patients.
Researchers from Seoul National University Hospital (Seoul, South Korea) and Pfizer Oncology (CA, USA) have published the results of a new test for the ALK mutation in a recent issue of the Journal of Molecular Diagnostics. In addition, a recent study in the Journal of Thoracic Oncology, suggests that immunohistochemistry (IHC) is a valid assay to be used alongside FISH to increase the availability of ALK mutation testing.
ALK fusions produce a constantly active tyrosine kinase, which is the driving mutation in approximately 3–5% of patients with non-small-cell lung carcinoma (NSCLC). Patients can be tested for fusion mutations in the ALK gene using FISH, IHC or reverse transcription PCR. NSCLC patients have much better treatment options once they have been identified as having an ALK gene fusion, such as the drug crizotinib (XALKORI®), which has been approved by the US FDA and is currently going through Phase III trials to specifically treat NSCLC patients who are ALK positive.
A number of ALK fusion detection tests have been clinically certified, including a FISH-based test, which was approved by the FDA for the crizotinib clinical trials. Although the FISH assay has received authorization, it has a number of limitations, including its complexity, cost and level of throughput.
“The FISH assay has undergone extensive validation in the clinical setting and is currently the gold standard for ALK fusion detection” said the lead investigators of the Journal of Molecular Diagnostics study, Dong-Wan Kim from the Seoul National University Hospital and Mao Mao from Pfizer Oncology. They continued, “A disadvantage of this diagnostic assay, however, lies in the fact that the signal can be subtle and consequently hard to interpret, requiring specialized technical expertise. It is also considerably more expensive compared with IHC and reverse transcription PCR. An optimal assay should therefore not only be sensitive and specific, but also be economical, easy-to-perform, preferably automated and readily adaptable to workflows of clinical service laboratories.”
The group developed a novel test detecting ALK fusions by multiplexed transcript profiling using a gene-expression platform from NanoSting® Technologies (WA, USA). The assay was tested on 66 NSCLC samples and showed encouraging results in being able to detect low-level ALK fusions. In addition, the samples found to be ALK-positive by the assay responded well to crizotinib.
Speaking to Pharmacogenomics, Mao explained the authors‘ hopes for the new test: “This cost-effective and easy-to-perform test could potentially increase the number of patients identified who could benefit from crizotinib treatment.” The authors are now working on a larger validation study and are also looking for probes to other ALK fusion variants.
The investigators of the Journal of Molecular Diagnostics study concluded, “While further testing on a larger sample size is needed for this assay to be considered in clinical practice, we have demonstrated that it offers a cost-effective, easy-to-perform, high-throughput and formalin-fixed, paraffin-embedded compatible screening alternative for detecting ALK fusions.”
The second study, published in the Journal of Thoracic Oncology, used currently available antibodies to ALK and IHC to screen 377 cases of early-stage NSCLC for ALK mutations. The results from IHC were compared with FISH. Two of the antibodies had 100% sensitivity and 87.5% specificity, with no false-positive results.
Christopher Conklin, lead author of the study (University of British Columbia, Vancouver, Canada) explained the findings of this study to Pharmacogenomics: “We have shown that certain commercially available ALK antibodies can be used to screen all patients with NSCLC for ALK mutation in a cost-effective and time-efficient manner.” Conklin continues that, “Cases suspicious for ALK mutation by antibody testing can then have confirmatory FISH testing, and if positive, receive crizotinib.”
The authors of this study have the same aim as Mao and Kim; according to Conklin, “Currently, the expense of FISH testing precludes it from being universally available to all patients. By implementing ALK antibody testing, all patients with NSCLC could be screened, and those with ALK mutations could receive the benefits of crizotinib therapy.”
Conklin described ideas for further research coming from this study: “It would be interesting to follow the response of these patients who receive crizotinib. It would also be interesting to see how this proposed diagnostic algorithm model, combining ALK antibody and FISH testing, functions in practice.”
Mao further explained the wider implications of crizotinib treatment: “Crizotinib has changed the paradigm of cancer drug development by targeting a molecularly defined subtype of NSCLC, despite its rarity, so we expect to see more of these kinds of therapies being developed and approved.” The development of cost-effective, sensitive and specific assays is important in the appropriate use of targeted therapies.
– Written by Theo B ond & Alisa Crisp
Sources: Lira ME, Kim TM, Huang D et al. Multiplexed gene expression and fusion transcript analysis to detect ALK fusions in lung cancer. J. Mol. Diagn. 15(1), 51–61 (2013); Conklin CM, Craddock KJ, Have C, Laskin J, Couture C, Ionescu DN. Immunohistochemistry is a reliable screening tool for identification of ALK rearrangement in non-small-cell lung carcinoma and is antibody dependent. J. Thorac. Oncol. 8(1), 45–51 (2013); Elsevier press release: www.elsevier.com/about/press-releases/research-and-journals/novel-test-identifies-patients-most-likely-to-benefit-from-alk-inhibition-therapy.
The results from a Phase II clinical trial for the chronic myeloid leukemia (CML) drug, ponatinib (Iclusig™), were presented recently at the 54th ASH Annual Meeting and Exposition (GA, USA) by researchers from The Anderson Department of Leukemia at the University of Texas (TX, USA).
The T315I mutation is a single base pair substitution in the ABL gene and is found in up to one-fifth of CML patients. This mutation has been deemed ‘invincible‘ because of its resistance to all previously approved Bcr–Abl inhibitors. Ponatinib was developed by ARIAD (MA, USA) as a multitargeted kinase inhibitor and has been found to be effective against all isoforms of Bcr–Abl.
The findings from the Phase II clinical trial for ponatinib showed that all 12 enlisted patients, who had the T315I mutation, displayed a complete hematologic response with no trace of CML cells in their blood after treatment. Of these patients, 75% had a complete cytogenetic response showing no CML cells in their bone marrow.
The trial‘s prinicipal investigator Jorge Cortes, Professor at The University of Texas MD Anderson Cancer Center, said: “Ponatinib is a promising new treatment for patients who have run out of options and its activity against a variety of mutations and in patients with no known mutations suggests a broad range of efficacy for this drug.”
In addition to being able to treat CML patients with the T315I mutation, ponatinib is effective in CML patients with a range of mutations. Of the 65 patients who had relapsed, had resistant CML or had Philadelphia chromosome-positive acute lymphoblastic leukemia, 67% achieved a complete cytogenetic response.
Since the encouraging results were presented at the meeting, the US FDA has fast tracked ponatinib‘s approval, 3 months ahead of schedule. Richard Pazdur, director of the FDA‘s Office of Hematology and Oncology Products in the Center for Drug Evaluation and Research, said: “The approval of Iclusig is important because it provides a treatment option to patients with CML who are not responding to other drugs, particularly those with the T315I mutation who have had few therapeutic options.”
– Written by Theo Bond
Sources: Anderson Cancer Center press release: www.mdanderson.org/newsroom/news-releases/2012/chronic-myeloid-leukemia.html; US FDA press release: www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm332252.htm
A consortium of international investigators from several institutions have presented their encouraging findings at the recent American Society of Hematology annual meeting (GA, USA), for a new drug, quizartinib, which has been developed for acute myeloid leukemia (AML) patients who have a specific FLT3 mutation.
A number of AML patients develop secondary tumors after going into remission due to a mutation in the FLT3 enzyme, which is involved in cell growth. The lead investigator of the study, Mark Levis, professor of oncology and medicine at Johns Hopkins (MD, USA), described the study, saying: “We can put two-thirds to three-quarters of adults with AML into remission with chemotherapy, but there is a 50% chance of the disease coming back, which usually ends up being fatal.”
A proportion of these patients have a mutation in the FLT3 gene, which codes for an enzyme that initiates bone marrow stem cell division. This mutation means the FLT3 enzyme is continuously active, causing a constant proliferation of leukemia cells.
Levis continued, saying “A FLT3 internal tandem duplication (ITD) mutation tells us that, typically, patients will need very intensive chemotherapy just to achieve a remission, and then the disease will regrow quickly. So, we have learned to try to perform a bone marrow transplant soon after we get the patient into remission, before the cancer relapses.”
The clinical trial involved 137 AML patients, the majority of whom had the FLT3-ITD mutation, who were treated with the new drug (AC220), which blocks the FLT3 enzyme.
Of the patients who have the FLT3-ITD mutation, 44% had some form of complete remission and 47 of the 137 patients were able to have a bone marrow transplant after being treated with quizartinib. Levis concluded, “Many patients in this trial were able to go on to receive a potentially life-saving bone marrow transplant. It caught us by surprise how well it works.”
Following these successful results, Ambit Biosciences (CA, USA), the developers of quizartinib, are planning larger Phase III trials.
– Written by Theo Bond
Source: Johns Hopkins News Release: www.hopkinsmedicine.org/news/media/releases/more_than_a_third_of_high_risk_leukemia_patients_respond_to_an_experimental_new_drug
A study presented at the recent 2012 CTRC-AACR San Antonio Breast Cancer symposium (TX, USA) by researchers from the Mayo Clinic (FL, USA) has identified 32 genes with an association with the treatment outcome of the breast cancer drug trastuzumab (Herceptin®).
Trastuzumab is an antibody that is used in combination with chemotherapy to treat HER2-positive breast cancer patients; however, in approximately one-quarter of patients the cancer returns. The underlying reason for this recurrence has been unknown so treating physicians have not been able to identify which patients will and will not respond to trastuzumab before prescribing it.
The study carried out by the Mayo clinic in conjunction with the Dana-Farber Cancer Institute (MA, USA), the University of Washington (WA, USA), Ventana Medical Systems-Roche (AZ, USA) and Indiana University (IN, USA) used gene-expression profiling to predict the outcome of trastuzumab treatment. Their results identified 27 genes that are significantly associated with a good outcome for chemotherapy with trastuzumab treatment. In addition, they also discovered five genes that were concurrent with a poor response to trastuzumab.
Edith Perez, deputy director at large of the Mayo Clinic Comprehensive Cancer Center and director of the Breast Cancer Translational Genomics Program at Mayo Clinic, described the results by saying, “These findings are also getting us closer to unraveling the biological factors that are relevant to patient outcome, which will help us improve clinical care.”
The group has already discovered the function of some of the identified genes and have been able to group the genes depending on their action. Some of the roles of the genes include cell cycle, gene transcription, cell receptor signaling and cell death. However, further analysis will be required to understand the biological workings of HER2-positive tumors and to elucidate why some are unresponsive to trastuzumab.
The major long-term goal for this research will be the development of a test that will allow doctors to identify the genetic make up of their patients‘ tumors and tailor the optimal personalized breast cancer therapy for them. “We are on our way to developing a predictive test that can define the right treatment for individual patients, and that is very exciting,” concluded Perez.
The researchers hope to confirm their findings by collaborating with other groups who are carrying out trastuzumab clinical trials in Europe and elsewhere in the USA.
– Written by Theo Bond
Source: Mayo Clinic press release: www.mayoclinic.org/news2012-jax/7194.html