Phar Lap and the Treatment of Leukemia

250px-Phar_LapPhar Lap (1926-1932) was a thoroughbred horse bred in New Zealand. After winning the Melbourne Cup and 37 other races, his victory at the Agua Caliente racecourse in Tijuana, Mexico, established the track record in 1932.

With each victory, his detractors became more strident. He was even the target of an assassination attempt. To prevent him from winning (and thereby disrupting the betting odds) officials would add lead bricks to his saddle. On the occasion of the Melbourne cup of 1930 he carried 138 pounds of lead, yet won the race. A quote from the Sydney Morning Herald dated Wednesday, November 5, 1930, read, “The question was not which horse could win, but could Phar Lap carry the weight. Could he do what no other horse before him had done?”

It appeared that the one thing that race officialdom feared above all else, was a horse that could consistently beat the field and win the race.

The tale of Phar Lap was brought to mind after a colleague forwarded a paper published in the journal Leukemia on August 10, 2012: “The use of individualized tumor response testing in treatment selection: second randomization results from the LRF CLL4 trial and the predictive value of the test at trial entry.” (E Matutes, AG Bosanquet et al, Leukemia, Letter to the Editor.)

Published as a letter to the editor, the paper describes correlations between the TRAC (tumor response to antineoplastic compounds) assay, a short-term suspension culture cell death laboratory assay (very similar to our work) and clinical response, time to progression and overall survival in patients with chronic lymphocytic leukemia (CLL) who received chemotherapy as part of the LRF CLL4 trial conducted in England between 1999 and 2004.

The initial trial was a blinded correlation between laboratory assay results and patient response to one of three treatment regimens. An examination of the data reveals a clear and statistically significant correlation between drug sensitivity and overall survival (p = .0001). The 10-year survival of drug sensitive patients was 28 percent, while the 10-year survival for drug resistant patients was 12 percent.

Significant correlations with survival were observed for known prognostic factors like 17p and 11q deletion, as well as IGHV mutational status. Correlations were also observed between the TRAC assay results and these prognostic factors.

The report goes on to describe a second randomization that took place at the time of disease progression, either failure of first-line therapy or reoccurrence within 12 months. In this part of the study, 84 relapsed patients were allocated to standard therapy and their outcomes were compared with 84 patients allocated to treatment guided by the TRAC assay. The drugs tested in the assay-directed arm included chlorambucil, cytoxan, methylprednisolone, prednisolone, vincristine, doxorubicin, mitoxantrone, 2CDA, fludarabine and pentostatin. In vitro resistance for combinations was defined as resistance to all constituent drugs in the combination, while drug sensitivity was defined as TRAC-assay sensitivity for any of the drugs used in combination. No discussion of synergy analysis was included.

In examining this study, I cannot help but be reminded of Phar Lap. First, marshaling a study of 777 CLL patients, and conducting 544 TRAC analyses, is a phenomenal undertaking for which these authors should be commended.

Second, the observation of a significant correlation between laboratory assay results and overall survival, as well as the biological implications of this platform’s capacity to correlate with molecular markers is a demonstrable and noteworthy success, however unheralded.

Where the analogy with poor Phar Lap’s struggles, weighted down with lead, becomes most poignant is the final portion of the study wherein 84 patients received assay-directed therapy. To wit, we must remember that in 2012, drug refractory CLL remains an incurable malignancy (with the exception of a small subset of successfully transplanted patients) and that no chemotherapy-alone trial has provided a survival advantage in this group. But this only begins to explain this trial’s results.

Among the virtually insurmountable hurdles that these investigators were forced to confront was the fact that fully 52 percent of the standard treatment arm group were destined to receive fludarabine. This drug, the current gold standard for previously treated patients who fail chlorambucil (constituting 73 percent of the patients in this part of the trial), has an objective response rate of 48 – 52 percent in this population. As the drug would likely be identified as active in vitro as well, this had the impact of pitting the assay arm and the standard arm against one another, frequently using exactly the same treatment.

While this does not mean that the assay arm could not succeed, it does have an enormous impact upon the sample size calculations used to determine the number of patients required to achieve significance.  No pharmaceutical company would ever allow a registration trial to be conducted against an “unknown” control arm, particularly one using the same therapy as the study arm – not ever! Despite these burdens, the assay-directed arm had a superior one-year survival, while virtually all other trends favored the group who received assay-selected therapy. The results of this study are worthy of recognition and further support the clinical relevance, predictive validity and importance of functional analyses. Yet, this interesting study in CLL is unceremoniously relegated to the status of a Letter to the Editor in Leukemia. Perhaps, like Phar Lap, no one really wants to upset the odds.

A Tale of Two Trials

As I read through the November 10 issue of the Journal of Clinical Oncology there were two very different but highly instructive reports.

They first examined the impact of gemtuzumab ozogamicin for patients with acute myeloid leukemia. The second involved the incorporation of bevacizumab and erlotinib into the treatment of Stage III NSCLC in combination with radiation.

By way of introduction, gemtuzumab ozogamicin (GO) is an anti CD33 antibody linked to the highly toxic chemical calicheamicin. Calicheamicin, a member of enendyne class, is among the most toxic substances known to man. By linking this poison to an antibody directed against leukemia cells, it was reasoned that this novel conjugant would provide an effective therapy for leukemia. And indeed it did. But despite compelling science and what appeared to be initially good results (particularly in older patients with AML), and FDA approval for the agent, the drug was withdrawn from the market. Now, with the publication of a new study from the United Kingdom, GO is once again in the limelight as its inclusion in induction therapy resulted in a statistically significant three-year relapse-free survival advantage (p=.0007) and three year overall survival advantage (p=.05).

It appears, with regard to GO, that the clinical trial process failed to identify the clinical utility of an active and novel form of therapy for a potentially lethal disease.

The second article of interest regards a pilot study that incorporated an anti-VGEF antibody (bevacizumab) with EGFR TKI (erlotinib) along with chemotherapy and radiation. In this trial the objective response rate of 39 percent, median progression-free survival of 10.2 months and median overall survival of 10.4 months, were not demonstrably superior to contemporary results, yet toxicity was significantly enhanced. The investigators recommended against further exploration of this combination. Here the aggressive integration of targeted and conventional therapies proved a misadventure.

While these two reports are very different, they represent similar failings of the contemporary clinical trial process. The GO experience reflects the failure to identify efficacy due to contemporary clinical trial’s dilution of the benefit in select candidates, mixed in the overall population, with limited responsiveness to the agent. The second trial represents clinicians’ desire to engage in theoretically attractive clinical trials only to find that they reflect ineffective and/or more toxic treatment regimens.

On one hand, laboratory models that accurately identify responders can segregate those most likely to benefit from those who will not. GO represents just one of many interesting new classes of drugs for whom selective methodologies could prove highly valuable. The lung cancer experience reflects the failure of the research community to dedicate adequate resources to predictive clinical models.

Combinations of chemotherapy with target therapies have been the subject of investigation in our laboratory for more than a decade. For example, we observed antagonism between platins and the EGFR antagonists (gefitinib and erlotinib) two years before publication of the unsuccessful INTACT I and II Trials and three years before the unsuccessful TALENT and TRIBUTE trials.

All four of these trials combined platin based doublets with EGF-TKI’s. More recently we successfully identified favorable interactions between erlotinib and VGEF inhibitors in individual patients that have provided durable responses in our NSCLC patients as first line therapy, now out to four and five years since diagnosis. These experiences represent opportunities to explore novel therapies and avoid inadvertent antagonisms and misadventures.  In the recent JCO, a good treatment was missed while a bad treatment was advanced.

Functional profiling through use of the EVA-PCD® assay may represent the “critical path” from bench to bedside that the deputy director of the Center for Drug Evaluation and Research at the Food and Drug Administration, Janet Woodcock has described as a crying need.

Stalking Leukemia Genes One Whole Genome at a Time

An article by Gina Kolata on the front page of the July 8, Sunday New York Times, “In Leukemia Treatment, Glimpses of the Future,” tells the heartwarming story of a young physician afflicted with acute lymphoblastic leukemia. Diagnosed in medical school, the patient initially achieved a complete remission, only to suffer a recurrence that led him to undergo a bone marrow transplant. When the disease recurred a second time years later, his options were more limited.

As a researcher at Washington University himself, this young physician had access to the most sophisticated genomic analyses in the world. His colleagues and a team of investigators put all 26 of the University’s gene sequencing machines to work around the clock to complete a whole genome sequence, in search of a driver mutation. The results identified FLT3. This mutation had previously been described in acute leukemia and is known to be a target for several available small molecule tyrosine kinase inhibitors. After arranging to procure sunitinib (Sutent, Pfizer Pharmaceuticals), the patient began treatment and had a prompt and complete remission, one that he continues to enjoy to this day.

The story is one of triumph over adversity and exemplifies genomic analysis in the identification of targets for therapy. What it also represents is a labor-intensive, costly, and largely unavailable approach to cancer management. While good outcomes in leukemia have been the subject of many reports, imatinib for CML among them, this does not obtain for most of the common, solid tumors that lack targets for these new silver bullets. Indeed, the article itself describes unsuccessful efforts on the part of Steve Jobs and Christopher Hitchens, to probe their own genomes for effective treatments. More to the point, few patients have access to 26 gene-sequencing machines capable of identifying genomic targets. A professor of bioethics from the University of Washington, Wiley Burke, raised additional ethical questions surrounding the availability of these approaches only to the most connected and wealthiest of individuals.

While brute force sequencing of human genomes are becoming more popular, the approach lacks scientific elegance. Pattern recognition yielding clues, almost by accident, relegates scientists to the role of spectator and removes them from hypothesis-driven investigation that characterized centuries of successful research.

The drug sunitinib is known for its inhibitory effect upon VEGF 1, 2 and 3, PDGFr, c-kit and FLT3. Recognizing the attributes of this drug and being well aware of C-KIT and FLT3’s role in leukemias, we regularly add sunitinib into our leukemia tissue cultures to test for cytotoxic effects in malignantly transformed cells.  The insights gained enable us to simply and quickly gauge the likelihood of efficacy in patients for drugs like sunitinib.

Once again we find that expensive, difficult tests seem preferable to inexpensive, simple ones. While the technocrats at the helm of oncology research promise to drive the price of these tests down to a level of affordability, everyday we wait 1,581 Americans die of cancer. Perhaps, while we await perfect tests that might work tomorrow, we should use good tests that work today.

American Association of Cancer Research 2012

In my last blog, I described my recent attendance at the American Association of Cancer Research (AACR) meeting held in Chicago. This is the premier cancer research convention for basic and translational research. The AACR was the original cancer research organization that pre-dated its sister organization – the American Society of Clinical Oncology. The focus of the AACR meeting is basic research and the presentations are often geared toward PhD level scientific discovery. I find this meeting the most informative for it provides insights into therapy options that may not arrive in the clinical arena for many years.

Among the presentations was a discussion of NextGen genomic analysis allowing an entire human genome to be sequenced within 24 hours. Mapping genetic elements has enabled investigators at the University of Pennsylvania to explore acute leukemia patients at diagnosis and at the time of recurrence. Based upon mutation analysis, different subsets of patients are observed. Mono and Oligo-clonal populations yield new subpopulations following cytoreductive therapy, wherein a small percentage of tumor cells survive and repopulate as the dominant clone.

The NextGen genomic analysis serves as the basis for new solid tumor studies in which breast biopsies are obtained, before and after therapy with aromatase inhibitors, to examine the clonality of the surviving populations.

William R. Sellers, MD, vice president of Novartis Institutes for BioMedical Research Oncology, described a high throughput robotic technology capable of conducting tens of thousands of combinatorial mixtures to determine drug interactions. What I found most interesting was the observation by this investigator that, “Cell culture remains the most effective means of testing drug combinations.” We agree wholeheartedly.

New classes of lymphoma therapies are in development that target B cell signaling pathways. A prototypic agent being Ibrutinib, the Bruton’s tyrosine kinase inhibitor.

Additional developments are examining SYC as a target for small molecule inhibitors.
Our growing understanding of immune regulation is enabling investigators like James Allison to trigger tumor specific immunity. Agents like ipilumimab (AntiCTLA4), combined with other classes of small molecules and/or antibodies directed toward CD28, PD1, and ICOS regulation have the potential to change the landscape in diseases that extend from melanoma to prostate and breast.

The meeting had innumerable sessions and symposia that were geared toward or touched upon the field of metabolomics. As cells jockey for survival they both up- and down-regulate pathways essential to not only energy production but to the biosynthesis of critical metabolic intermediates. The regulation of PKM2 (pyruvate kinase isoenzyme) is now recognized as a pivotal point in the cell’s determination of catabolism (energy production), over anabolism (biosynthesis), with Serine concentrations playing an important regulatory role.

The PI3K pathway is an area of rapidly growing interest as new compounds target this key regulatory protein complex. Both selective and non-selective (pan PI3K) inhibitors are in clinical testing. Paul Workman’s group was honored for their seminal work in this and related areas of drug development. We reported our findings on the dual PI3K/mTOR inhibitor BEZ235 (Nagourney, RA et al Proc AACR, 2586, 2012).

The double-edged sword of immune response was deftly covered by Dr. Coussens who described the profound tumor stimulatory effects of T-cell, B-cell and Macrophage infiltration into the tumor microenvironment. Small molecules now in development that down-regulate macrophage signaling may soon show promise alone or in combination with other classes of drugs.

The RAS/RAF pathway becomes ever more complex as we begin to unravel the feedback loops that respond to small molecule inhibitors like Erlotinib or Vemurafanib. Investigators like Dr. Neal Rosen from Memorial Sloan-Kettering Cancer Center have long argued that simple inhibition at one node in a cascade of signaling pathways will absolutely change the dynamic and redirect up and down stream signals that ultimately overcome inhibition. Strategies to control these “resistance” mechanisms are being developed. Once again we find that simple genomic analyses underestimate the complexity of human systems.

Among the regulatory topics at this year’s meeting was a special symposium on the development and testing of multiple novel (non-FDA approved) compounds in the clinical trial setting. There will need to be a new level of cooperation and communication forged between academia, regulatory entities and the pharmaceutical industry if we are to move this process forward. I am encouraged by the early evidence that all three are recognizing and responding to that reality.

The themes of this year’s meeting included:
1. A renewed focus on the biochemistry of metabolism
2. Clear progress in field of tumor immunology
3. The growing recognition that human tumors exist as microenvironments and not isolated single cells.

We are particularly gratified by the last point.

Our EVA/PCD focus on human tumor aggregates (microspheroids) isolated directly from patients as the most accurate models for chemotherapy selection and drug discovery appears to be gaining support.

Faster than the Speed of Light

Last week, scientists at CERN, the European particle physics laboratory located outside Geneva, Switzerland, conducted an experiment, the results of which now challenge one of the most fundamental principles of modern physics. I speak of Albert Einstein’s 1905 declaration that the speed of light is an absolute and that nothing in the universe could travel faster.

E = MC2, the principle under which nuclear energy and weapons have been developed, as well as all of the corollaries of the theory of relativity were called into question when a series of sub atomic particles, known as neutrinos traveled from Switzerland to Italy at a speed that was 1/60 of a billionth of a second faster than the speed of light. What has followed has been a flurry of interest by departments of physics all over the world. Confronted with this new finding, these investigators will diligently seek to reproduce or refute the findings.

This was not the first time that someone challenged the primacy of Einstein’s 1905 theory. Indeed, during the 1930s, for largely political and anti-Semitic reasons, the Nazi party attempted to disprove Einstein. Yet, all of the political meanderings, personal vendettas and intellectual jealousy could not unseat Einstein’s guiding principle. That is, until objective evidence in the form of the CERN experiments came to the fore.

Science — however lofty — and scientists — however highly regarded — dwell in the same realm as all the rest of us mere mortals. Their biases and preconceived notions often cloud their vision. Comfortable with a given paradigm, they hold unyieldingly to its principles until they are forced, however unwillingly, to relinquish their belief systems in favor of a new understanding. I write of this in the context of laboratory-based therapeutics – a field of scientific investigation that has provided firm evidence of predictive validity. These technologies have improved response, time to progression and survival for patients with leukemia, ovarian, breast and lung cancers, as well as melanoma and other advanced malignancies. Thousands of peer-reviewed published experiences have established the merit of human tumor primary cultures for the prediction of response. Investigations into the newest classes of targeted therapies are providing new insights into their use and combinatorial potential.

Yet,  while the physicists of the world will now rise to the challenge of data, the medical oncologists and their academic counterparts refuse to accept the unimpeachable evidence that supports  the validity of assay-directed therapy. Perhaps if our patients were treated at CERN in Geneva,  their good outcomes would receive the attention they so richly deserve.

Is Rationed or Rational Medical Care In Our Future?

We are witness to a sea change in medicine. Doctors and nurses are being replaced by “healthcare providers;” medical judgment is being phased out in favor of therapeutic algorithms; and the considered selection of treatments is giving way to rigid therapy guidelines. All the while, the regulatory environment increasingly precludes the use of “off label” drugs. It is understandable why insurers, governmental entities and hospital chains might welcome these changes. After all, once therapies have been reduced to standardized formulae, one can predict costs, resource allocations and financial exposures to the twentieth decimal place. For many medical conditions, these approaches will provide adequate care for the majority of patients.

But, what of the outliers? What of those complicated disease entities like cancer, whose complexity and variability challenge even the best minds? How do we bang the round peg of cancer therapy into the square hole of formulaic care?

There are several answers. The first is the least attractive: In this scenario, predicated upon cancer’s incidence in an older population, at the end or beyond their productive (and reproductive) years, we simply don’t allocate resources. Most civilized modern societies haven’t the stomach for such draconian measures and will seek less blunt instruments.

The second is a middle of the road approach. In this scenario, standardized guidelines that provide the same treatment to every patient with a given diagnosis are developed. Every medical oncologist knows the drill: FOLFOX for every colon cancer, Cytoxan plus Docetaxel for every breast cancer and carboplatin plus paclitaxel for ovarian cancer. The treatments work adequately well, the schedules are well established, the toxicities are well known and no one is cured. The beauty of this approach is that the average patient has an average outcome with the average treatment. By encompassing these regimens into standardized algorithms, we may soon be able to eliminate physicians entirely — first, with nurse practitioners and physician’s assistants and, ultimately, with computers. What is perhaps most surprising about this scenario has been the willingness of the medical oncology community to embrace it, a sort of professional self-induced extinction. At the time of this writing, this is the predominant model and is becoming increasingly entrenched under the auspices of NCCN and related guidelines. The operative term being guidelines, in as much as these “guidelines” are rapidly becoming “dictates.”

The final approach, and the one I find most appealing, is that which utilizes the clinical, scientific, laboratory and technical acumen of the physician to the maximum. Combining diagnostic skill with scientific insight, the physician becomes the captain of the ship, who must assume control from the autopilot once the vessel has entered the tempest and use his/her experience and training to guide the patient to a soft landing. This requires the capacity to think and demands an up-to-date knowledge of many disciplines. The judicious application of laboratory-directed approaches can further enhance the skillset, introducing objective data that is then used to guide drug and treatment selections. Predicated upon an understanding of the patient’s tumor biology, cancer therapy becomes an intellectual exercise that draws upon literature, and a knowledge of pharmacology and physiology. Adding the wealth of newly developed signal inhibitors to the mix only enhances the odds of a good outcome.

This approach improves responses and eliminates futile care. It provides patients the opportunity to participate in their own management. Correctly delivered, it would make available to every patient any FDA-approved drug. While it would seem to some that this would open the floodgates of drug use, I would strenuously disagree. It would instead limit drug administration to those patients most likely to respond, a goal currently pursed by virtually every major institution, yet accomplished by none. While a handful of targeted approaches have come to fruition in the last few years — erlotinib for EGFR mutation, and sunitinib in kidney cancers — most of the molecular profiling being done today doesn’t aid in the selection of therapy but instead provides negative information (e.g. RAS in colon cancer, ERCC1 over expression in lung) enjoining the physician against the use of a given agent but then leaving the unfortunate patient to fend for themselves amidst a panoply of randomly chosen options.

This is the approach that I have chosen to adopt in my own care of cancer patients. Our rapidly growing successes in ovarian, breast, lung, melanoma, leukemias and other diseases could and should serve as a model for others.

Is There a Role for Maintenance Therapies in Medical Oncology?

There is a long tradition of maintenance therapy in pediatric oncology. Children with acute lymphoblastic leukemia uniformly receive three stages of therapy: induction, consolidation, and finally maintenance. The maintenance stage consists of weekly, or even daily therapies.

The historical experiences of relapse in this population lead investigators to consistently expose these patients to drugs for a period of years. Despite the apparent success of this approach in childhood cancers, long-term maintenance therapy did not gain popularity in adult oncology. Why?

There are probably several reasons. One reason is that childhood leukemia is among the most chemo-responsive diseases in medicine. As such, there are many active drugs available for treatment and many non-cross-resistant maintenance schedules that can be employed.

A second reason is the relative tolerability of drugs like oral thioguanine or mercaptopurine that are used in chronic maintenance therapy. By contrast adult tumors rarely achieve complete remissions. The number of active drugs has historically been very limited and the tolerance of long-term treatments characteristically poor.

Despite this, there is an appealing rational for maintenance therapy. Once we recognized and incorporated the tenents of apoptosis and programmed cell death into cancer management, we were forced to reconsider many of the principles of older treatment protocols.

Conceptually, maintenance allows for a cytotoxic exposure when the cell enters a “chemosensitive” period in its life cycle.  Cancer cells that are “out surviving” their normal counterparts often do so in a quiescent stage (G0 Gx). In order to capture these cells, drugs must be present in the body when these cells awaken from their dormancy. As we have now achieved increasingly durable remissions in diseases like breast cancer, small cell lung and ovarian, we are confronting patients in long-term complete remission. When you add to this newfound population the availability of comparably mild agents, like the low dose Gemcitabine/Cisplatin doublet, we now have at our disposal active drugs that can be safely continued for long periods of time.

Using laboratory selection to identify first line (induction), second line (consolidation) and finally third line (maintenance) schedules, we can now offer our patients well-tolerated combinations that offer the hope of more durable remissions.

The GOG 178, in which continued taxol dosing provided more durable remission in ovarian cancer, provided the first inklings of this. Unfortunately, taxol is toxic. And the more durable remissions came at an increasingly high price: neuropathy, myelosuppression, alopecia, fatigue and malaise, which greatly limited the utility of this approach. Yet it does not limit its theoretical attractiveness as we continue to develop targeted agents with more selective activity and modified toxicity profiles. We anticipate maintenance therapies will become more widespread.

Based upon our experiences to date, we are successfully using this approach with our patients who achieve good clinical remissions.

Revolutionizing Treatment for Hairy Cell Leukemia Patients

Hairy cell leukemia is a rare malignancy characterized by spleen enlargement and progressive anemia and thrombocytopenia (low platelets). Bone marrow aspirations characteristically reveal a “packed marrow.” In the past, patients were often managed with splenectomy and oral chlorambucil. Response rates were low and complications, including infection and bleeding, often ensued.

The introduction of alpha interferon into the management of this disease by Gutterman and associates at M.D. Anderson, provided a meaningful advance during the 1980s. It was at this time that I was conducting a fellowship at the Scripps Clinic in La Jolla, Calif. I had the good fortune to work with Dennis Carson, MD, and his associate Bruce Wasson. They reasoned that the accumulation of deoxyadenosine, which occurred in children with Severe Combined Immunodeficiency (SCID) and was associated with the virtual annihilation of functional lymphocytes in affected patients, could be mimicked pharmacologically. By synthesizing a 2-chloro derivative of deoxyadenosine, they created 2-CDA.

Reasoning that the drug would be T-cell specific, they began early clinical trials in T-cell lymphoma patients. Dr. Carson kindly provided me with a small aliquot of 2-CDA for study in my laboratory. The activity observed in CLL, ALL and even AML, has since been confirmed. However, what was most interesting was the activity observed in the cells removed from the spleen of a hairy cell leukemia patient. The favorable dose response curve suggested to me that 2-CDA would be an active drug in this otherwise refractory malignancy. After my departure from Scripps Clinic, a junior fellow tested this response clinically, providing curative therapy in more than 90 percent of hairy cell leukemia patients. Today, a single cycle of 2-CDA is the treatment of choice for this disease, providing durable benefit in the majority of patients with minimal toxicity.

At Rational Therapeutics we continues to study novel drugs and combinations to examine their effectiveness in treating disease. Our unique ability to test malignant cells in their native state has enabled us to garner some of the most comprehensive results of any group. We will continue to identify new treatments as we move closer to finding cures for patients.