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PGx Highlights from the American Society of Clinical Oncology's 2013 Meeting

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The American Society of Clinical Oncology held its annual meeting June 1-5 in Chicago.
The following are abstracts presented at the meeting focused on pharmacogenomically guided treatment strategies.


Correlation of molecular alterations with efficacy of everolimus in hormone receptor–positive, HER2-negative advanced breast cancer: Results from BOLERO-2.

Researchers from Novartis and several academic institutions have conducted analysis to gauge genetic variations in a panel of cancer-related genes to gauge whether certain subgroups harboring these markers experience greater benefit from the mTOR inhibitor Afinitor (everolimus).

Gabriel Hortobagyi of University of Texas MD Anderson Cancer Center led a team of investigators in analyzing exon sequences and gene copy number variations in 182 cancer-linked genes using Foundation Medicine's next-generation sequencing test. Researchers then correlated genetic variations with patient outcomes in the Phase III BOLERO-2 study.

In that trial, postmenopausal women with hormone-receptor positive, HER2-negative advanced breast cancer who received Afinitor plus exemestane experienced more than a doubling of progression-free survival compared to just exemestane.

Testing tumor specimens from 227 patients with greater than 250x coverage by NGS revealed subgroups of patients whose response was defined by several genetic alterations. Patients with zero or only one genetic alteration in PI3K or FGFR pathways, or CCND1, derived the most treatment benefit from Afinitor.

"This is the first global registration trial in which efficacy-predictive biomarkers were explored by correlating broad genetic variations with clinical efficacy," Hortobagyi wrote in the abstract. "It demonstrated the feasibility of applying large-scale NGS and subsequent correlative analysis to such trials."

The study authors noted that the results are exploratory. "Their implication in understanding the interplay of multiple pathways in tumor cells and testing new hypotheses for targeted combination therapies in hormone receptor-positive, HER2-negative, breast cancer will be further investigated," they noted.


A phase II single-arm study of LDK378 in patients with ALK-activated (ALK+) non-small cell lung cancer (NSCLC) previously treated with chemotherapy and crizotinib (CRZ).

An international research team — led by Alice Tsang Shaw of the Massachusetts General Hospital Cancer Center and including researchers from Novartis Pharmaceuticals — gave a presentation on the company's ongoing Phase II multicenter trial of Novartis' novel, oral ALK inhibitor LDK378

According to the group's abstract, the trial is designed to evaluate the efficacy and safety of oral LDK378 in a 750 mg once-daily dose in non-small cell lung cancer patients deemed ALK-positive by the FDA approved FISH test.

There are currently no standard ALK-targeted treatments for cancers resistant to Pfizer's Xalkori (crizotinib), the group reported. Potentially, LDK378, which the researchers said has shown 20-fold greater potency than Xalkori in enzymatic assays, could serve as a treatment for those who develop resistance to the drug.

Overall, the study will enroll 137 patients who previously took Xalkori and had progression of their disease while on the drug, from 67 sites in 14 countries across Europe, Asia, and North America, according to the group's abstract. By February the trial had enrolled its first seven patients, and in the presentation of the study at the ASCO meeting, Shaw said enrollment is now up to 130 subjects.

The trial will assess the antitumor activity of LDK378 in terms of patients' overall response rate, as well as secondary endpoints including duration of response, time to response and radiological measures of overall response, and progression-free survival, overall survival, safety, and impact on patient-reported outcomes, according to the group's abstract.


Interim results of phase II study BRF113928 of dabrafenib in BRAF V600E mutation–positive non-small cell lung cancer (NSCLC) patients.

David Planchard from France's Institut Gustave Roussy presented interim results from the ongoing prospective Phase II study by French and US researchers working with GlaxoSmithKline, demonstrating that the company's BRAF inhibitor Tafinlar (darafenib) was associated with a disease control rate of 60 percent for patients with stage IV non–small cell lung cancer who carry the BRAF V600E mutation and whose disease progressed on prior chemotherapy.

The group's abstract describes results seen in the trial's first stage with 17 patients, and Planchard presented additional efficacy data at the meeting for the first 20 patients and safety data for the first 25. According to the abstract, the drug showed an overall response rate of 54 percent with the longest duration of response being 49 weeks for the first 17 patients.

In the presentation of the study, the group said they found that the overall disease control rate for the full 20 patients was 60 percent. Partial response was seen in 40 percent of patients, stable disease was seen in 20 percent of patients, and disease progression was reported for 30 percent of patients, the team reported.

According to the researchers, Tafinlar was also "generally well tolerated," with side effects at levels consistent with what has been seen previously. The initial results have been sufficiently positive for the team to move on to a planned second stage of the trial — expanding the cohort with another set of 20 patients.


An update on BREAK-3, a phase III, randomized trial: Dabrafenib (DAB) versus dacarbazine (DTIC) in patients with BRAF V600E-positive mutation metastatic melanoma (MM).

An international research team, led by Axel Hauschild of the University Medical Center Schleswig-Holstein in Germany, working with GlaxoSmithKline, shared updated survival results from the BREAK-3 trial comparing progression free survival of BRAF V600E-positive metastatic melanoma patients taking the company's BRAF inhibitor Tafinlar (dabrafinib) with survival of those treated with dacarbazine chemotherapy.

According to the groups' abstract, the results after the additional months of follow-up confirm the benefits of Tafinlar seen in earlier analyses on both progression-free survival and response rate.

The team reported that as of December 2012, median progression-free survival was 6.9 months in the Tafinlar group, and 2.7 months in the dacarbazine group. In December, the researchers said, 36 of 63 dacarbazine arm patients crossed over to the Tafinlar arm.

Additionally, the group was able to measure overall survival, reporting that median overall survival in the Tafinlar arm was over 18 months versus over 15 months in the dacarbazine arm, but the researchers said these results are most likely confounded by the crossover of patients from the chemo arm, who then began to be treated with Tafinlar.

The updated analysis found no significant changes in the drug's safety profile, according to the authors.


Efficacy of first-line bevacizumab (BEV)-based therapy for metastatic triple-negative breast cancer (TNBC): Subgroup analysis of TURANDOT.

An international research team with some financial ties to Roche, led by Moshe Inbar of the Central European Cooperative Oncology Group presented an exploratory triple-negative breast cancer subgroup analysis using data from the randomized phase III TURANDOT trial, concluding that patients with triple-negative cancer treated with Roche's Avastin (bevacuzimab) in the trial had one-year overall survival rates "up to 78 percent … among the highest seen [in triple-negative disease,]" according to the group's abstract.

TURNADOT is comparing first-line Avastin plus paclitaxel and Avastin plus capecitabine in HER2-negative metastatic breast cancer. Overall, the CECOG group's subgroup study looked at 130 patients with triple-negative cancer out of the trial's total of 561—63 of whom were randomized to the Avastin plus paclitaxel arm, and 67 of whom were randomized to the Avastin plus capecitabine arm.

According to the team's presentation, baseline characteristics were generally balanced between the trial's two treatment arms among this subgroup. The researchers reported that one-year overall survival rates for the triple-negative group were "up to 78 percent." Based on this, the authors suggested that Avastin-based therapy is a "valid option" considering the limited effective treatment options in triple-negative cancer.

Moreover, the group concluded that Avastin plus paclitaxel may be preferable over Avastin plus capecitabine based on one-year overall survival, progression-free survival, and objective response rate.

Overall survival for the paclitaxel arm at the one-year mark was 78 percent, while for the capecitabine arm, OS was only 63 percent.


Association between single nucleotide polymorphism (SNPs) of CYP3A4 and SLC28A3 and clinical outcome in metastatic breast cancer (MBC) patients receiving paclitaxel plus gemcitabine (PG) chemotherapy as first-line treatment.

Researchers from a larger group of South Korean medical centers led by Seock-Ah Im of the Seoul National University College of Medicine shared data from a study that found the SNP SLC28A3 can predict the clinical outcome of metastatic breast cancer patients treated with paclitaxel and gemcitabine combination chemotherapy, according to the team's abstract.

The group set out to study the potential predictive value of 27 SNPs in 15 genes in a subgroup of 85 patients from a 324-patient cohort in a trial of the combination chemotherapy regimen.

According to the authors, one SNP — SLC28A3, which participates in transcription — showed correlation with overall survival. Specifically, survival of the patients with CC and CT genotypes in SLC28A3 was significantly longer than that of the patients with TT genotype, the researchers reported.

Using Cox-regression analysis, the group also found that several clinical parameters, including young age, positive hormone receptor status, and the presence of hepatic metastases, were all also predictive of overall survival.

But after adjusting for these other potentially predictive factors, the prognostic value of SLC28A3 remained significant, according to the researchers. As a result, the group suggested that SLC28A3 may be an effective predictor of response to this combined chemotherapy regimen in metastatic breast cancer patients and warrants further study.

The researchers reported no affiliation with related industry.


First-in-human evaluation of CO-1686, an irreversible, selective, and potent tyrosine kinase inhibitor of EGFR T790M.

Lecia Sequist of the Massachusetts General Hospital led a team of researchers from the US and France, with funding and collaboration from Clovis Oncology, who presented data from an ongoing Phase I dose-finding clinical trial suggesting Clovis' investigational EGFR tyrosine kinase inhibitor CO-1686 "offers potential for improved activity and better tolerability over current EGFR TKIs, particularly in the treatment of T790M+ disease."

According to the team's abstract, existing EGFR tyrosine kinase inhibitors can become ineffective in NSCLC with the emergence of the T790M mutation in approximately 50 percent of patients. Additionally, current drugs cause significant side effects due to wild-type EGFR inhibition, which also compromise tolerability.

According to the group, CO-1686 is an orally active TKI that targets common activating EGFR mutations and T790M, while sparing wild-type EGFR.

The team reported that as of Jan. 18, 2013, 35 patients have been treated in the trial evaluating oral CO-1686 administered continuously in 21-day cycles for safety, pharmacokinetics, and efficacy. Doses up to 400mg three times per day have been tested so far, with a maximum tolerated dose not yet reached, the researchers said.

Reported adverse side effects of grade-three or higher included hypoglycemia and hyperglycemia — each in one patient, while side-effects typical of wild-type EGFR inhibition, such as rash and diarrhea, have not yet been observed in the trial, according to the researchers.

At a dose of 900mg once per day, two of three patients showed clinical benefit after two cycles of the drug, including one with "clinically-relevant [18 percent] tumor shrinkage" and another patient with successful stabilization of a pleural effusion," the team reported. At 300mg twice daily, one patient exhibited "significant tumor shrinkage" of 29 percent after two cycles of treatment.

According to the group, these initial results suggest that Clovis' drug has potential for better effectiveness and tolerability, especially for treatment of T790M-positive disease, "an area of high unmet clinical need."


BATTLE-2 program: A biomarker-integrated targeted therapy study in previously treated patients with advanced non-small cell lung cancer.

Researchers led by Vassiliki Papadimitrakopoulou of the University of Texas MD Anderson Cancer Center reported data from the BATTLE-2 clinical study, which aims to identify response markers associated with EGFR, PI3K/AKT, and MEK inhibitors. After stratification based on identified markers based on an adaptive randomization design, researchers aim to improve survival in refractory NSCLC patients treated with these medications.

The four-arm, open-label, Phase II trial has so far enrolled 219 refractory NSCLC patients who failed to respond to at least one prior line of treatment, and 124 patients have been randomized. After entry in the study, patients are evaluated for biomarkers. Based on their KRAS status, they are randomized to one of four trial arms to receive treatment with Tarceva (erlotinib); Tarceva plus the AKT inhibitor MK-2206; MK-2206 plus the MEK inhibitor selumetinib; and Nexavar (sorafenib).

Tarceva is sold by Roche subsidiary Genentech and Nexavar is co-marketed by Bayer and Onyx Pharmaceuticals. MK-2206 is being developed by Merck, and selumetinib is being developed under a collaboration between AstraZeneca and Array Biopharma.

The study is seeking to gauge eight-week disease control in four arms and in two stages. In the first stage patients are randomized based on KRAS mutation status, but patients whose tumors at baseline have EGFR mutations or EML4/ALK translocations are not included. In Stage 2 of the study, the biomarker-based predictive model is further refined and 400 patients are randomized based on a new algorithm.

So far researchers have reported that 100 patients are evaluable for the eight-week disease control endpoint.

BATTLE-2 follows BATTLE-1, data from which was published in Cancer Discovery in 2011. In BATTLE-1, 255 patients were adaptively randomized to four arms —Tarceva; AstraZeneca's investigational Zactima(vandetanib); Tarceva plus Eisai's Targretin(bexarotene); or Nexavar — based on their biomarker profiles, which included EGFR mutations and/or copy number, KRAS/BRAF mutations, VEGF/VEGFR-2 expression, and RXRs/Cyclin D1 expression and copy number. Primary end point was 8-week disease control, which served as a surrogate for outcome.

In the BATTLE trials researchers analyze tumor samples from patients collected in "real time." Many of the drugs being explored in BATTLE-1 failed clinical trials for lung cancer when investigated without the help of a biomarker strategy. For example, Tarceva has been approved for use in NSCLC – most recently for first line use in NSCLC patients with EGFR mutations – but Targretin, Nexavar, Zactima all failed in phase III trials that did not use biomarkers to select patients for treatment.

In comparison, MK-2206 and selumetinib, which are included in BATTLE 2, are also being studied in various biomarker-based trials involving NSCLC patients. BATTLE-2 is slated for completion in 2017.

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