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Commentary on Pharma & Biotech Oncology / Hematology New Product Development

Posts tagged ‘vemurafenib’

“RAF inhibitors (vemurafenib and dabrafenib) have profound clinical activity in patients with BRAF-mutant melanoma, but their therapeutic effects are limited by the emergence of drug resistance.”

Solit and Rosen (2014)

For today’s post on Science Fridays, I wanted to take a look at an overview paper, published in Cancer Discovery, from two researchers in the metastatic melanoma field who have been looking at multiple mechanisms of resistance.  It’s an important topic because while we have seen incremental improvements in outcomes for this disease, the 5-year survival rate is still rather poor with only 10–20% of metastatic patients still alive by then.  This is not to disparage the efforts of scientists, clinicians or companies working in this space, far from it, but there is is clearly a need for new therapies, strategies and combinations, given the high unmet medical need that exists.

We still have a long way to go in moving the survival needle dramatically.

It wasn’t until I searched for related blog posts to link to this one that I realised how much we have already covered on this topic! Regular readers will recall discussions here on PSB on various combinations such as:

  1. RAF + MEK inhibitors (downstream resistance)
  2. RAF + PI3K-AKT-mTOR inhibitors (cross resistance)
  3. RAF + CTLA–4 checkpoint inhibitors (anti-tumour immunity)

to name a few examples.

We have seen that adding a MEK inhibitor to dabrafenib e.g. trametinib can overcome resistance temporarily and add a few extra months before the resistance sets in again. Similarly for PI3K inhibitors tested to date. Adding ipilimumab, an anti-CTLA–4 checkpoint inhibitor held much promise, but the combination was abandoned with the emergence of unexpected liver toxicity.

Results thus far suggest that something else is acting as an escape route, thereby enabling the tumour to continue driving oncogenic addiction to BRAF.

The $64K questions are what is happening and what can we do about it?

We also need to remember that clinical research advances piecemeal based on evidence from preclinical reseach, so we see the logical evolution of BRAF monotherapy -> combos with downstream (MEK) or upstream (NRAS) targets in same pathway -> combos with diagonal (PI3K) pathways etc.

What Solit and Rosen have done is put a nice summary together of the state of play in this disease and the paper (see References below) is well worth reading.

Their main assertion is interesting, namely:

“The common feature of each of these mechanisms of resistance is that they result in activation of ERK signaling that is insensitive to the RAF inhibitor. Thus, RAF inhibitor resistance is often associated with maintenance of activation of the oncogene-driven pathway.”

Two recent papers are cited in support of this theory from Shi et al., (2014) and Allen et al., (2014) – see References below for additional background reading. Both studies used patient samples to look at clonal evolution and the genetic landscape in advanced melanoma. It’s actually quite amazing what unbiased exome sequencing can uncover at the molecular level, not least are the development of new mutations and other functional alterations.

The Shi et al., (2014) study was briefly summarised by Solit and Rosen:

“Multiple biopsies were obtained at different times or from disparate locations from several patients, and more than a single lesion in the ERK pathway was identifi ed in multiple patients typically within
different tumor biopsies.”

They went to note:

“A detailed phylogenetic analysis of multiple progressive lesions from a subset of these patients suggested branching evolution of tumors in which the development of genetic diversity was not linearly associated with time.”

Previously, a case report found distinct mechanisms of BRAF inhibitor resistance were present in two different progressing lesions from a single patient, so the work of Shi et al., (2014) is consistent with this finding. It blows my mind that different lesions in the same patient might behave completely differently though – imagine trying to devise an appropriate and effective clinical strategy in these cases?!

Allen et al’s (2014) work also involved whole exome sequencing (WES) from patient samples:

“WES was performed on paired pretreatment and progression samples collected from 45 patients, of whom 14 developed resistance soon after initiation of therapy (within 12 weeks). They also detected several resistance mechanisms that had been previously identified to confer RAF inhibitor resistance, including mutations in NRAS , MAP2K1, and NF1 and BRAF amplification.”

A third important study in this area from Wagle et al., (2014) adds to the weight of evidence with new mutations developing. Solit and Rosen continued the story:

“Consistent with the preclinical studies highlighted above demonstrating that MEK1 and MEK2
mutations can confer RAF and MEK inhibitor resistance, a MEK2 Q60P mutation was identifi ed in 1 of 5 patients studied. Of greater surprise to the investigators, one patient had a BRAF splice variant lacking exons 2–10 and a second patient had BRAF amplification.”

By now, you can see the sheer variety of changes and adaptations taking place in different studies around the world in some of the top melanoma labs. What do they have in common though?

“One hypothesis to explain this result is that increased abundance of the oncogenic driver (in this case BRAF) in response to prolonged drug treatment results in increased flux through the ERK pathway and restoration of ERK activity above the threshold required for inhibition of cell proliferation.”

The next challenge is to figure how we can approach better therapeutic index and shutting down of the pathways?

“The results suggest that the early adaptive response of BRAF -mutant cells to ERK pathway inhibition may promote the selection of resistant clones that harbor additional genomic events that
confer higher levels of RAF inhibitor resistance. The data also support combinatorial approaches that attenuate the adaptive response, including the addition of a PI3K or AKT inhibitor to the RAF and MEK (or ERK) inhibitor combination.”

The problem with this approach though, is that the neither the BRAF nor PI3K inhibitors have been able to reach or go beyond the single agent dosing schedules:

“As previous attempts to combine MAPK and PI3K pathway inhibitors have been limited by overlapping toxicities, upfront testing of intermittent treatment schedules should be considered.”

This is the also approach that Das Thakur suggested in her work presented at AACR last year, and subsequently published in Nature, to delay the development of resistance to vemurafenib.

I do think this one area where we may well see new trials evolve in advanced melanoma, so we will have to wait for new data before we can see if the strategy is successful at delaying the emergence of resistant clones. It is good to see the evolution of solid preclinical and translational evidence from patient biopsies helping to inform future clinical trial strategies.

In the meantime, the next major milestone I’m waiting for is on Roche/Genentech’s MEK inhibitor, cobimetinib (GDC–0973), which is due to report combination data with vemurafenib (continuous dosing) later this year. It will be interesting to see if this inhibits MEK more completely than trametinib and whether the combination has a better initial outcome than dabrafenib plus trametinib, which added about two to three months of extra survival over dabrafenib alone.

References:

ResearchBlogging.orgSolit DB, & Rosen N (2014). Towards a Unified Model of RAF Inhibitor Resistance. Cancer discovery, 4 (1), 27–30 PMID: 24402945

Shi H, Hugo W, Kong X, Hong A, Koya RC, Moriceau G, Chodon T, Guo R, Johnson DB, Dahlman KB, Kelley MC, Kefford RF, Chmielowski B, Glaspy JA, Sosman JA, van Baren N, Long GV, Ribas A, & Lo RS (2014). Acquired Resistance and Clonal Evolution in Melanoma during BRAF Inhibitor Therapy. Cancer discovery, 4 (1), 80–93 PMID: 24265155

Van Allen EM, Wagle N, Sucker A, Treacy DJ, Johannessen CM, Goetz EM, Place CS, Taylor-Weiner A, Whittaker S, Kryukov GV, Hodis E, Rosenberg M, McKenna A, Cibulskis K, Farlow D, Zimmer L, Hillen U, Gutzmer R, Goldinger SM, Ugurel S, Gogas HJ, Egberts F, Berking C, Trefzer U, Loquai C, Weide B, Hassel JC, Gabriel SB, Carter SL, Getz G, Garraway LA, Schadendorf D, & Dermatologic Cooperative Oncology Group of Germany (DeCOG) (2014). The Genetic Landscape of Clinical Resistance to RAF Inhibition in Metastatic Melanoma. Cancer discovery, 4 (1), 94–109 PMID: 24265153

Wagle N, Van Allen EM, Treacy DJ, Frederick DT, Cooper ZA, Taylor-Weiner A, Rosenberg M, Goetz EM, Sullivan RJ, Farlow DN, Friedrich DC, Anderka K, Perrin D, Johannessen CM, McKenna A, Cibulskis K, Kryukov G, Hodis E, Lawrence DP, Fisher S, Getz G, Gabriel SB, Carter SL, Flaherty KT, Wargo JA, & Garraway LA (2014). MAP Kinase Pathway Alterations in BRAF-Mutant Melanoma Patients with Acquired Resistance to Combined RAF/MEK Inhibition. Cancer discovery, 4 (1), 61–8 PMID: 24265154

Das Thakur M, Salangsang F, Landman AS, Sellers WR, Pryer NK, Levesque MP, Dummer R, McMahon M, & Stuart DD (2013). Modelling vemurafenib resistance in melanoma reveals a strategy to forestall drug resistance. Nature, 494 (7436), 251–5 PMID: 23302800

One of the interesting themes for that emerged for me at AACR this year was the amount of effort that is being expended on strategies to overcome drug resistance. This was particularly noticeable in metastatic melanoma and non-small cell lung cancer (NSCLC).  More on lung cancer in another post, as today I want to focus on melanoma.

In the advanced melanoma, vemurafenib is given to patients with the BRAFV600E mutation, which occurs in approximately 50% of patients. This oncogene drives activity of the tumour, but inhibition with vemurafenib (Zelboraf) has shown some remarkable effects, as the stunning before and after photos from Levi Garraway’s group demonstrate.

The challenge, however, is that adaptive or acquired resistance can occur in response to treatment and patients sadly find their melanoma returning after approximately 6-9 months on continuous daily therapy.

At last year’s ASCO, we saw that adding a MEK inhibitor such as trametinib to a BRAF inhibitor such as dabrafenib added around an extra 3 months over single agent BRAF therapy before the resistance set in and the disease returned, sometimes with a deadly vengeance.

I’ve written here on this blog about numerous mechanisms of resistance in advanced melanoma from MEK to COT and others (see related posts below for background reading).

The big question at this AACR was how is the field progressing with new research?

Sometimes, we have to go back to the lab to study animal models of resistance before returning to the clinic with new ideas.

Screen Shot 2013-04-15 at 2.54.50 PMThat’s what a young Novartis Postdoctoral fellow from NIBR, Meghna Das Thakur, did. She asked critical questions and attempted to answer them in a series of elegant experiments with mice as well as retrospectively test the concept in patient data. The cool thing is that while many of the oral sessions were taken up by the Major League researchers is that it’s also nice to see up and coming young scientists present some nicely done research.

What Dr Thakur did was really interesting…

Her hypothesis was simple – that resistant tumours are ‘less fit’ than sensitive cells and have a selective disadvantage over sensitive cells in the absence of drug.

If this were true then we would expect to see dependence on drug for growth of resistant tumours in xenografts, much as we do in humans, with vemurafenib. The data clearly showed that vemurafenib resistant tumours were dependent on drug for growth. They also observed that:

1) p-ERK levels increased following withdrawal of vemurafenib in resistant tumours
2) There was a great deal of heterogeneity in the mechanisms of resistance

The key question then becomes how can we use this information to prevent resistance?

One way to explore this is to look at selective pressure, since vemurafenib is usually given continuously…

  • Treating continuously means that selective pressure enriches resistant cells
  • However, withdrawing the drug means that resistant cells suffer a fitness deficit

Essentially, the researchers noted that, “alternating the selective pressure prevents the emergence of a resistant population.”

In comparing continuous vs intermittent dosing, two things could be concluded from the model:

1) Resistant tumours emerge more rapidly under continuous dosing with vemurafenib
2) Intermittent dosing in multiple tumor xenograft models forestalled resistance

What can we learn from retrospective patient data?

What they did next was to look at computed tomography (CT) scans analysed for evidence of vemurafenib-dependence in patients treated with vemurafenib in the BRIM-3 and vemurafenib safety study, which were identified from the clinical trials database at the Royal Marsden Hospital. In particular, they focused on patients who stopped treatment because of progressive disease (PD).

Of 42 patients identified, 19 of these had CT scans performed after cessation of vemurafenib available for review, while 23 patients did not have a CT available for review and in 16 patients this was because of rapid PD.

For each of those 19 patients with a post-vemurafenib CT, the total tumour volume on three consecutive CT scans was recorded:

  • The CT performed prior to stopping vemurafenib
  • The CT performed when progressive disease was diagnosed and vemurafenib stopped
  • The CT performed after vemurafenib was stopped and prior to the initiation of further therapy

They found that 14 of the 19 patients experienced decreased tumour growth rate following cessation of vemurafenib, supporting the hypothesis that resistant tumours emerge more rapidly under continuous dosing with vemurafenib.

In this model, it is clear that intermittent dosing prolongs survival, but what is the underlying mechanism, and what does this mean for future treatment of patients and also clinical trial designs?

From this initial work it was clear that the MOA is not yet fully understood and further bench work will be needed to elucidate the mechanisms involved.  We don’t yet know, as the researchers point out, whether:

“Does resistance come from a clonal population or is it an adaptation or re-wiring of a selected few cells?”

What was clearer though, is that new clinical research will be needed to evaluate the potential for intermittent vs continuous dosing in patients, particularly in combination:

  • Will there be greater selective pressure from BRAF + MEK inhibitor combinations vs BRAF alone?
  • Identify combination partners that could be used during BRAF inhibitor holiday.

Overall…

I thought this was a very nice piece of well thought out research, perhaps one of my favourites from the AACR meeting this year.  Critically, we saw that the preclinical mouse xenograft model predicted a clinically-relevant resistance mechanism. Removal of drug from resistant cells leads to MAPK pathway hyper-activation and resistant cells experience a fitness deficit. Cycling the mice on and off therapy led to better outcomes than if they were dosed continuously, thereby giving us a new strategy to consider in melanoma patients.

The main impact of this preclinical study is that future clinical research in advanced melanoma should investigate the value of intermittent dosing strategies to improve patient outcomes.

The work turns the old concept of continuous dosing 365/24 on its head – suppressing the BRAFV600E oncogene continuously in melanoma may not necessarily be the best strategy in terms of superior outcomes.

This this does NOT mean that ALL tumours will behave in a similar fashion and intermittent dosing should be tested first in clinical trials where there is sufficient scientific evidence to warrant it.  If I were a patient, considering drug holidays without any evidence of effectiveness would NOT be a good idea.

I’m really looking forward to seeing the results of future combination trials with intermittent dosing to see if outcomes are indeed improved beyond would we currently see with continuous dosing either alone or in combination.

 

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Photo Credit: Sally Church Pharma Strategy BlogFollowing on from my preview of the 2012 American Society of Clinical Oncology (ASCO) meeting, I am now working through updates on some of the hot topics.

I’m delighted to announce The Chemical & Engineering News blog ‘The Haystack’, have published my second guest post on advances in metastatic melanoma.

This is a devastating disease that has seen very few advances over the last decade since the approval of dacarbazine (DTIC) until last year when the FDA approved two new therapies in vemurafenib (Zelboraf) for patients with the BRAFV600E mutation and ipilumumab (Yervoy), an immunotherapy that targets CTLA4.

Since then, we’ve realised that the inevitable happens – patients tumours become resistant to single agent TKI therapy because adaptive resistance pathways are activated and cross-talk with the MAPK kinase pathway often occurs.  The question of how we can improve on the encouraging results seen so far was explored in new trials in Chicago?

For those of you interested, you read my summary on The Haystack about the new developments in metastatic melanoma from ASCO, which includes dabrafenib, trametinib, anti-PD-1 and others.

For those who missed it, I also wrote a guest post about the ASCO 2012 data on overcoming resistance in non-small cell lung cancer.

May I take this opportunity to wish all my American readers a very enjoyable July 4th Independence Day weekend!

 

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There’s been quite a flurry of commercial news on the Pharma front this morning, with Amgen buying Micromet (whose leading product is blinatumumab in ALL) and Celgene announcing their acquisition of Avila Therapeutics who have a Bruton Kinase Inhibitor (BTK) AVL-292 in phase IB development for lymphomas, which was all the rage at the recent American Society of Hematology (ASH) meeting last month.

The big news for me today, though, wasn’t the commercial acquisitions but a gem of a paper relating to science and its significance for future cancer treatment.

One of the unsolved scientific conundrums that arose in my interview with Dr Gordon Mills (MDACC) at the European Multidisciplinary Cancer Congress (EMCC) meeting in Stockholm last September centred around the RAS pathway, and the BRAFV600E mutation, in particular.

Dr Mills astutely noted that while vemurafenib (Zelboraf) has shown activity in patients with advanced melanoma with the BRAFV600E mutation, he raised the important question why did we not see similar activity in mutated colon cancer?  Of course, one obvious conclusion might be that the target isn’t critical to the tumour’s survival… or is it?  The challenge though, is that these patients do particularly poorly, and usually that is a sign that the mutation is actively driving aberrant activity. Therein lies the quandary, leaving many researchers such as Dr Mills puzzled at the discrepancy and asking why?

This week I’ve been doing a series on colorectal cancer and it is quite by coincidence that today we learn more about the science of colon cancer and BRAFV600E mutations since Pralahad et al., (2012) have just published a Letter in Nature explaining that their research actually suggests that resistance mechanisms might be one of the culprits:

“We performed an RNA-interference-based genetic screen in human cells to search for kinases whose knockdown synergizes with BRAF(V600E) inhibition. We report that blockade of the epidermal growth factor receptor (EGFR) shows strong synergy with BRAF(V600E) inhibition.”

This finding surprised me because melanoma typically has low levels of EGFR expression, unlike more epithelial cancers:

“We compared EGFR expression in a panel of BRAF(V600E) mutant melanoma, colon cancer and thyroid cancer cells. Melanoma cell lines indeed express low levels of EGFR.

So what actually happens in melanoma?

“Mechanistically, we find that BRAF(V600E) inhibition causes a rapid feedback activation of EGFR, which supports continued proliferation in the presence of BRAF(V600E) inhibition.”

Ah, our old friend, feedback loops!  These have an uncanny knack of popping up in advanced cancers, as the cancer attempts to ensure it’s survival and overcome the targeted therapy, causing adaptive resistance to treatment in their wake.

You may be wondering how common is this mutation in colon cancer then? Well, Pralahad et al., (2012) observed:

“Our data suggest that BRAF(V600E) mutant colon cancers (occur in) approximately 8–10% of all colon cancers.

Note: bracketed bold addition mine.

What does this data tell us?

In short, a combination of vemurafenib and an EGFR inhibitor, such as erlotinib, cetuximab or gefitinib, might be a useful clinical approach to try therapeutically in patients with colon cancer harbouring the BRAFV600E mutation.  Of course, Roche/Genentech have both vemurafenib and erlotinib (Tarceva) in their portfolio, so it would be interesting to see whether proof of clinical concept could be established quickly in a phase I clinical trial.  EGFR inhibitors tend to be rather quirky though, and it remains to be seen whether a small molecule (erlotinib, gefitinib, afatinib) or a monoclonal antibody (cetuximab, pantitumumab) would be the ideal partner for vemurafenib in this setting.

While there is much yet to be done in R&D to advance the scientific research, this important finding teaches us that there is hope for this subset with a generally poorer prognosis yet.

I look forward to following the future clinical progress to see if a viable new combination treatment emerges in BRAF V600E mutated colon cancer – watch this space!

References:

ResearchBlogging.orgPrahallad, A., Sun, C., Huang, S., Di Nicolantonio, F., Salazar, R., Zecchin, D., Beijersbergen, R., Bardelli, A., & Bernards, R. (2012). Unresponsiveness of colon cancer to BRAF(V600E) inhibition through feedback activation of EGFR Nature DOI: 10.1038/nature10868

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“Ipilimumab is not recommended for the treatment of advanced (unresectable or metastatic) malignant melanoma in people who have received prior therapy.

The Committee was satisfied that ipilimumab meets the criteria for being a life-extending, end-of-life treatment and that the trial evidence presented for this consideration was robust.

The Committee acknowledged that few advances had been made in the treatment of advanced melanoma in recent years and ipilimumab could be considered a significant innovation for a disease with a high unmet clinical need.

Despite the combined value of these factors the Committee considered that the magnitude of additional weight that would need to be assigned to the QALY gains for people with advanced (unresectable or metastatic) melanoma would be too great for ipilimumab to be considered a cost-effective use of NHS resources.”

NHS NICE Guidance

In other words, it’s too expensive and the NHS doesn’t want to pay the £80K ($120K) sticker price. This news is no great surprise given the cost-benefit ratio when considering that there is no way to tell who might benefit most from treatment upfront.

The is, however, a huge difference between hope and false hope, as NPR Shots astutely noted when discussing Avastin in breast cancer earlier this week and in some ways that sentiment applies here too. By this I mean it would be much more compelling to both patients and NICE if an oncologist could talk about a new therapy in specific and useful terms.

Examples of doctor-patient conversations about treatment in the near future might look more like this….

Either:

“You have an 70-80% chance of responding to this therapy because you have X (mutation, translocation, biomarker etc), where this drug has been shown to be highly effective and extends life by over 2 years in many of our advanced patients with this disease to date.”

Or:

“This drug may do more harm than good in your case, as it has been shown to effectively target X (mutation, translocation, biomarker etc), which you do not have, and therefore, are unlikely to respond. I believe it would be better to consider these alternatives in your situation… “

We all know about heterogeneity – it’s the very underpining of what makes a cancer survive despite our best efforts to tame it until we can subset into more homogenous and predictable groups.  This means that offering a broad therapy to all patients with a given advanced cancer without any idea of its predictive value is fast becoming a misnomer in today’s world of emerging targeted therapies.  Now, manufacturers (marketers even) might think it’s better not to ‘limit’ their market opportunity, but the reality is many healthcare systems are looking at ways to limit treatments to where it’s needed most, not only for cost reasons, but also to direct resources where they are more likely to work. The current model is not sustainable in the long run.

Of course, if a predictive biomarker was available to determine which patients are more likely to respond to ipilimumab, then the QALY calculation would be considerably different, and possibility even within the realms of the current guidelines.

That’s a whole different ballgame, but hopefully one that will begin to emerge as we have seen with new targeted therapies such as vemurafenib (Zelboraf) in BRAF V600E malignant melanoma, crizotinib (Xalkori) in ALK-positive advanced lung cancers and everolimus (Afinitor) in combination with exemestane in ER/PR+ HER2- breast cancers that have relapsed after initial aromatase inhibitor therapy.

It will be interesting to see how NICE handles all of those situations in the future, since they are all targeted agents showing a significant impact on a patients ability to live longer,with a more precise, and therefore, limited patient definition.  As a Brit and a scientist, I may have reasonable expectations that NICE will make a rational and logical decision in the face of limited resources, but this is also tinted with a large dose of healthy scepticism after the trastuzumab (Herceptin) debacle in HER2-positive breast cancers that lead to the utterly ridiculous and unfair post code lottery in the UK.

We are not talking absolute costs here, but the relative costs of seeing real efficacy benefits of six months or more in those patients most likely to respond, while at the same time giving an offering that truly extends life in a meaningful fashion without exposing too many to the toxic side effects of a given treatment. Dealing with cancer is tough enough without being treated with a regimen that had absolutely no hope of helping people live longer and feel better.

This morning the FDA approved vemurafenib (Zelboraf), along with it’s companion diagnostic, for the treatment of metastatic melanoma in patients with the BRAF V600E mutation.

This is great news!

The approval has been granted ahead of time, as correctly mentioned in the Reuters article recently. This means we now have two new therapies for the treatment of metastatic melanoma after ipilimumab (Yervoy) was approved in March.

These two new drugs have been rapidly approved within the space of a couple of months following the presentation of the data at the ASCO plenary session in June.

Very little has changed in this landscape since the original approval of dacarbazine (DTIC) many years ago, but the good news is that oncologists now have two new agents to consider for treatment in 2011, which is very much a grand cru year for melanoma.

Zelboraf (link to PDF of the PI) differs from Yervoy in that it is not an immunotherapy to CTLA4, but a small molecule tyrosine kinase inhibitor that targets BRAF and more specifically, one of the mutations driving the disease, V600E.  This mutation is seen in approximately half of patients with metastatic melanoma.  The companion diagnostic (from Roche’s diagnostic division) will enable oncologists to test patients upfront and determine who should receive the therapy since the clinical results have only been demonstrated in those with the mutation.

The hot question is what is the price?

Well, according to Roche/Genentech, the monthly price of Zelboraf will be $9,400 and assumes an average of ~6 months of treatment based on the progression-free survival (PFS) data reported in the phase III BRIM3 (5.3 months) and phase II BRIM2 (6.1 months) studies. The overall survival had not been reached at that time. This means the course of treatment with Zelboraf will be approximately $56,400, but will obviously depend on how long it is taken for.  The comparative cost of treatment for ipilimumab for four infusions is $30K per infusion or $120K per full course.

In addition, the cost of the diagnostic test will likely vary depending upon the laboratory, but it is expected will be determined by the test volume and contract framework established with the laboratory.  The Average Selling Price (ASP) for the cobas BRAF test will be ~$120-150 per test in the US, which is very reasonable.

All in all, news like this will bring a smile to many today – it’s always good to hear of new drugs that make a difference to the lives of cancer patients.

 

 

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A Reuters press release on vemurafenib (Zelboraf) caught my eye this morning, suggesting that it might be approved in BRAFV600E metastatic melanoma by the FDA might be “imminent” according to an unnamed source and much earlier than the expected PDUFA date in November October 28th (now confirmed by Roche/Genentech).

If so, that’s very good news.

However, what really caught my eye was a quote from a spokesperson at Roche Diagnostics, suggesting that the BRAFV600E test would could around $150.  That’s lower than I was expecting, although no doubt it will be considerably offset by the cost of vemurafenib itself.

It was also good to hear recently that Roche and BMS, the manufacturers of ipilimumab (Yervoy), have now met to discuss and finalise the much anticipated combination trial of Zelboraf and Yervoy.  It will be interesting to see if the combination will extend survival even further in patients with the V600E mutation.  There’s a long way to go before the results bear fruit, as an early dose finding and tolerability study will be the first step in the process.

Of course, pricing and reimbursement will be key, given that Yervoy was launched recently with a $120K price tag for four infusions.  On the 2Q earnings call the other week, BMS announced that the launch was going well and uptake was strong.  It is given as a 3mg infusion every three weeks for 4 cycles, over a 3 month period.  It will be interesting to see what the Zelboraf monthly price will be, assuming it successfully garners approval.   Should the combination work out in the future, the cost of treating metastatic melanoma will likely become even more expensive despite only small incremental survival benefits.

 

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Last month an interesting article was published in The New England Journal of Medicine describing how BRAFV600E mutations may have a key role to play in hairy cell leukemia (HCL), which came out around the same time as the European Hematology Association (EHA) meeting that I attended in London.  The news certainly caused a buzz at the conference!

Source: Wikipedia

Hair cell leukemia is a fairly rare type of leukemia that affects B cells (lymphocytes), which are distinguished by their hairy like appearance under the microscope because they have fine projections coming from their surface.

Over the past year, we have heard much about how the BRAFV600E mutation plays a critical role in melanoma and the progress with the testing of a specific inhibitor, vemurafenib (PLX4032), in the clinic, leading to some initial clinical success in this indication.  What’s particularly interesting about the NEJM article is that it describes, for the first time, how the BRAFV600E mutation may be a key genetic alteration in HCL.

The researchers used Sanger sequencing to undertake an extensive analysis of the genome in normal and HCL peripheral blood samples. The findings were also validated in additional patients with HCL (n=47).  The results were a little surprising:

“Whole-exome sequencing identified five missense somatic clonal mutations that were confirmed on Sanger sequencing, including a heterozygous mutation in BRAF that results in the BRAF V600E variant protein.”

The mutation was only found in patient samples who had HCL, not other types of leukemia or lymphomas:

“None of the 195 patients with other peripheral B-cell lymphomas or leukemias who were evaluated carried the BRAF V600E variant, including 38 patients with splenic marginal-zone lymphomas or unclassifiable splenic lymphomas or leukemias.”

Some immunohistologic and Western blot studies, were performed.  They found that:

“HCL cells expressed phosphorylated MEK and ERK (the downstream targets of the BRAF kinase), indicating a constitutive activation of the RAF–MEK–ERK mitogen-activated protein kinase pathway in HCL.

In vitro incubation of BRAF-mutated primary leukemic hairy cells from 5 patients with PLX-4720, a specific inhibitor of active BRAF, led to a marked decrease in phosphorylated ERK and MEK.”

PLX-4720 is another BRAF inhibitor that Plexxikon have in development in addition to the original one, PLX-4032 that became vemurafenib.

Now, while is promising evidence that needs to be researched further, we must exercise caution.  Remember that just because a mutation exists, does not mean that it is a key driver.  We saw this with colon cancer and BRAFV600E mutations – where vemurafenib had little of no effect in patients, despite promising preclinical data – a stark contrast to the results in metastatic melanoma!  Why does the same target produce entirely different results when inhibited by an effective agent?  One reason could be that that BRAF is a passenger not a driver in colon cancer.

In the meantime, I will be keenly following any progress with testing of specific BRAF inhibitors for patients with hairy cell leukemia to see whether it will be a useful clinical approach in managing the disease or not.

 

References:

ResearchBlogging.orgTiacci, E., Trifonov, V., Schiavoni, G., Holmes, A., Kern, W., Martelli, M., Pucciarini, A., Bigerna, B., Pacini, R., Wells, V., Sportoletti, P., Pettirossi, V., Mannucci, R., Elliott, O., Liso, A., Ambrosetti, A., Pulsoni, A., Forconi, F., Trentin, L., Semenzato, G., Inghirami, G., Capponi, M., Di Raimondo, F., Patti, C., Arcaini, L., Musto, P., Pileri, S., Haferlach, C., Schnittger, S., Pizzolo, G., Foà, R., Farinelli, L., Haferlach, T., Pasqualucci, L., Rabadan, R., & Falini, B. (2011). Mutations in Hairy-Cell Leukemia New England Journal of Medicine, 364 (24), 2305-2315 DOI: 10.1056/NEJMoa1014209

Well, after just getting back from the American Society of Clinical Oncology (ASCO) meeting in Chicago, I’m heading off to Europe for the European Hematology Association (EHA) meeting – no rest for the wicked!

ASCO was a rather flat meeting this year – the stars were undoubtedly the imatinib 36 vs 12 month data in adjuvant GIST (clearly superior) and Roche/Plexxikon/Daiichi Sankyo’s vemurafenib in BRAF V600E metastatic melanoma. The ipilimumab data was strangely disappointing in the upfront setting – only 2 months improvement in survival when added to DTIC.

On the Sarcoma front, the catch-all nature of the study came back to haunt Merck with an improvement in PFS but no overall survival benefit for ridaforolimus as maintenance therapy after 1-3 cycles of chemotherapy. That filing will likely result in a highly charged ODAC meeting debating the merits of some awkward results.

Ovarian cancer data was a mixed bag – olaparib continues to look promising in this setting, although the Avastin OCEANS data caught a few people by surprise – yet another PFS endpoint met but no overall benefit in survival and the expected incidence in bowel perforations. I think this will likely be reserved for high risk women, if used.

There was a lot of interesting/promising data in phase II, which are too numerous to mention right now – check back as I will be adding some notes on some of the emerging compounds that I liked.

Meanwhile, I’m aggregating the tweets from the hematology meeting using the #EHA11 hashtag – you can track them in the widget below if interested in following along remotely. Most of the tweets from me will likely be on leukemias, lymphomas and multiple myeloma.

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Two of the most dynamic cancer markets at the moment are prostate cancer and metastatic melanoma, which is great news considering that neither has had much attention over the last decade compared to breast and lung cancers.

My colleague has posted an overview of what’s going on in advanced prostate cancer today, which you may be interested in checking out pre-ASCO.  However, what excited me this morning were announcements from BMS and Roche declaring their intent to pursue combination trials in BRAF metastatic melanoma with their therapies ipilimumab (Yervoy) and vemurafenib (PLX4032).

This is really great news, and a very logical approach that is well worth evaluating.

I’m delighted to see the two companies seeking to work together on this to see if the combination can improve outcomes further than what we have seen for vemurafenib alone, which already showed impressive responses in poor prognosis patients.

How vemurafenib works in BRAF V600E metastatic melanoma

Vemurafenib has been shown to target the BRAF V600E mutation, as you can see in the graphic.

Ipilimumab is an immunotherapy that targets the CTLA-4 antigen and was approved by the FDA in March as a treatment option for newly diagnosed patients with metastatic melanoma.

A phase I/II trial is planned initially, which is a relatively low risk study – if the results look good we will hopefully see a larger scale phase III trial emerge.  If not, at least we will know a quick answer on the combination.

Meanwhile, these two drugs will be presented in the plenary session at ASCO this weekend comparing either to the current standard of care, dacarbazine (DTIC), in advanced newly diagnosed metastatic melanoma.

I’m really looking forward to writing more on those trials on Monday morning – so do check back then for an update of the phase III data!

 

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