Examination of Xalkori activity in human tumor primary culture micro-spheroids

gdpawel said:

Functional Profiling Leads to Accurate Genomic Findings

Robert A. Nagourney, M.D.
Medical & Laboratory Director
Rational Therapeutics

The 2013 American Society of Clinical Oncology annual meeting, held May 31 – June 1, in Chicago, afforded the opportunity to report three studies.

The first, “An examination of crizotinib activity in human tumor primary culture micro-spheroids isolated from patients with advanced non-small cell lung cancer,” reports our experience using the EVA-PCD platform to examine the drug crizotinib. This small molecule originally developed as an inhibitor of the oncogenic pathway MET, was later found to be highly active in a subset of cancer patients who carried a novel gene rearrangement for anaplastic lymphoma kinase (ALK). It was this observation that lead to the drug (sold under the name Xalkori) being approved for the treatment of advanced ALK positive lung cancer. The subsequent observation that this same drug inhibited yet another gene target known as ROS-1 found in a subset of lung cancer patients, has led to its use in this patient population.

Our exploration of crizotinib activity identified a series of patients who received the drug and responded dramatically. This included both ALK positive and ROS-1 positive patients. One patient however, appeared highly sensitive to the drug in our studies, but was found negative for the ALK gene rearrangement by genomic analysis. We repeated our functional analysis only to the find again, the same high degree of crizotinib sensitivity. I felt confident the patient should receive crizotinib, but at the time the drug was not yet commercially available and he didn’t qualify for the protocols, as he was ALK negative.

I scoured the country looking for a way to get the patient treated with crizotinib. From Sloan Kettering to UCLA, no one could help. And then, in collaboration with my abstract co-author Ignatius Ou from UC Irvine, we decided to repeat the ALK analysis. That proved to be a very good idea. For the patient was indeed positive for ALK gene rearrangement by second analysis and subsequently responded beautifully to a treatment for which he would not otherwise qualify. Once again, phenotype trumped genotype.

A final patient in the series represented a particularly interesting application of functional analysis. The patient, a young woman with an extremely rare pediatric sarcoma, had failed to respond to multiple courses of intensive chemotherapy and her family was desperate. As she approached the end of her third year in high school, it looked unlikely that she would reach her senior year. A portion of her tumor was submitted for analysis. The results confirmed relative resistance to chemotherapeutics, many of which she had already received and failed, but showed exquisite sensitivity to crizotinib. Indeed, our inclusion of crizotinib in the analysis reflected our intense effort to identify any activity for this previously refractory patient.

We reported our findings to the pediatric oncologist and encouraged them to consider an ALK rearrangement analysis, despite this particular pathway not being on anyone’s radar prior to our study. The result – a positive gene rearrangement. This led to a successful petition to the drug company for the use of this agent for an off-label indication. The response was prompt and dramatic, and remains durable to this day, nearly a year later. Again, the phenotypic analysis guided us to the correct genomic finding.

Note: Xalkori (crizotinib) is prescribed for previously-treated anaplastic-lymphoma-kinase-positive advanced non-small-cell lung cancer (NSCLC). It is a tyrosine kinase inhibitor, which works by blocking enzymes which can stimulate cancers to grow. The drug blocks a specific enzyme, anaplastic lymphoma kinase (ALK), which is present in some 3%-5% of NSCLC tumors estimated to be ALK-positive.

Another of the functional cytometric profiling labs has reported out positive for Xalkori (crizotinib) killing tumor cells and killing endothelial cells, with absolutely brilliant responses, in some ALK translocation negative lung cancer patients.

Robert A. Nagourney, M.D.
Medical & Laboratory Director
Rational Therapeutics

Targeted therapies, named for their capacity to target specific tumor related features, are being developed and marketed at a rapid pace. Yet with an objective response rate of 10 percent (Von Hoff et al JCO, Nov 2011) reported for a gene array/IHC platform that attempted to select drugs for individual patients that have a long way to go before these tests will have meaningful clinical applications.

Dr. Robert Nagourney is medical and laboratory director at Rational Therapeutics, Inc., in Long Beach, California, and an instructor of Pharmacology at the University of California, Irvine School of Medicine. He is board-certified in Internal Medicine, Medical Oncology and Hematology. He did an analysis of using the ALK gene test vs a cell-based functional profiling test for Xalkori (crizotinib).

"Let’s examine the more established, accurate and validated methodologies currently in use for patients with advanced non-small cell lung cancer. I speak of patients with EGFR mutations for which erlotinib (Tarceva) is an approved therapy and those with ALK gene rearrangements for which the drug crizotinib (Xalkori) has recently been approved.

The incidence of ALK gene rearrangement within patients with non-small cell lung cancer is in the range of 2–4 percent, while EGFR mutations are found in approximately 15 percent. These are largely mutually exclusive events. So, let’s do a “back of the napkin” analysis and cost out these tests in a real life scenario.

One hundred patients are diagnosed with non-small cell lung cancer.
• Their physicians order ALK gene rearrangement $1,500
• And EGFR mutation analysis $1,900
• The costs associated $1,500 + $1,900 x 100 people = $340,000
Remember, that only 4 percent will be positive for ALK and 15 percent positive for EGFR. And that about 80 percent of the ALK positive patients respond to crizotinib and about 70 percent of the EGFR positive patients respond to erlotinib.

So, let’s do the math.

We get three crizotinib responses and 11 erlotinib responses: 3 + 11 = 14 responders.
Resulting in a cost per correctly identified patient = $24,285

Now, let’s compare this with an ex-vivo analysis of programmed cell death.

Remember, the Rational Therapeutics panel of 16+ drugs and combinations tests both cytotoxic drugs and targeted therapies. In our soon to be published lung cancer study, the overall response rate was 65 percent. So what does the EVA/PCD approach cost?

Again one hundred patients are diagnosed with non-small cell lung cancer.
• Their physicians order an EVA-PCD analysis $4,000
• The costs associated: $4,000 x 100 people = $400,000
• With 65 percent of patients responding, this
constitutes a cost per correctly identified patient = $6,154

Thus, we are one quarter the cost and capable of testing eight times as many options. More to the point, this analysis, however crude, reflects only the costs of selecting drugs and not the costs of administering drugs. While, each of those patients selected for therapy using the molecular profiles will receive an extraordinarily expensive drug, many of the patients who enjoy prolonged benefit using EVA/PCD receive comparatively inexpensive chemotherapeutics.

Furthermore, those patients who test negative for ALK and EGFR are left to the same guesswork that, to date has provided responses in the range of 30 percent and survivals in the range of 12 months.

While the logic of this argument seems to have escaped many, it is interesting to note how quickly organizations like ASCO have embraced the expensive and comparatively inefficient tests. Yet ASCO has continued to argue against our more cost-effective and broad-based techniques."

Xalkori in NSCLC

http://cancerfocus.org/forum/showthread.php?t=3306

rdn2blazer said:

So what does this all mean???

I have the ALK mutation with my lung cancer. I was my cancer doctor's first case with ALK mutation in 30+ years as a cancer doctor. All I know is I've had to take this drug for a year, will be done with this last bottle of meds thank god. I hope to hell it works. Going to be pissed if this comes back again. This medication costs $11,169.82 dollars PER MONTH for 60 pills. Thats insane!!! Thank god for Insurance. My co-pay is $200 a month.

All the gene mutation study, that was done to find the ALK, can tell you is whether or not the cancer cells are "potentially" susceptible to this mechanism of attack (theoretical analysis). It cannot tell you if the targeted drug will actually work for your cancer cells, or not.

The incidence of ALK gene rearrangement in patients with NSCLC is in the range of 2-4 percent, while EGFR mutations are found in approximately 15 percent.

These are almost always mutually exclusive events (i.e. mutations of only 1 of the 2 genes occur within any individual tumor), but not always. Never say never about the possibility of having both an EGFR mutation and an ALK rearrangement.

A study published in the International Association for the Study of Lung Cancer's Journal of Thoracic Oncology (JTO) researchers have found that tumors with ALK rearrangements can harbor additional mutations.

And there are lots of things which determine if drugs work, beyond the existence of a given target. Does the drug even get into the cancer cell? Does it get pumped out of the cell? Does the cell have ways of escaping drug effects? Can cells repair damage caused by the drug? 

And probably most important, do "combinations" of drugs work in ways which can't be predicted on the basis of static gene expression patterns?

The idea of searching for clinical responders by testing for a single gene mutation seems like a nice theoretical idea, but you may have to test for dozens of protein expressions that may be involved in determining sensitivity/resistance to a given drug. Because if you miss just one, that might be the one which continues cancer growth.

There are options. One of them requires some tumor specimen to be secured to pre-test your cancer cells "actually" against other compounds and combinations and can recommend them, all from one test.

Going after a surgical/biopsy specimen has a role in eliminating ineffective agents and avoid unnecessary toxicity and in directing "correct" therapy. The time and energy required to conduct an excisional biopsy pales in comparison to the time, energy and lost opportunities associated with months of ineffective, toxic therapy.

What does it all mean? Targeted therapy is still trial-and-error treatment. Be vigilant and research as much as you can about your particular cancer.