Science & Medicine

Response to attacks on interferon — An open letter

An Open Letter to the MPN Community in the United States

Hasselbalchby Dr. Hans Carl Hasselbalch
Roskilde Hospital, Professor, Department of Hematology, University of Copenhagen

Dear Friends, Colleagues and Patients…

About 25 years ago recombinant interferon (IFN) was used successfully for the first time in the treatment of essential thrombocythemia and a few years later in the treatment of polycythemia vera and hyperproliferative myelofibrosis. Since then many studies have confirmed that IFN benefits a large number of MPN patients. (Throughout this letter IFN stands for rIFNα, or recombinant interferon-alpha.)

In this context I am worried  by the reported claims by Dr. Ayalew Tefferi that IFN is no better than HU and busulphan in the MPNs. If Tefferi has said so, it is problematic that a colleague, who may be aware of his great impact on the “scientific community ” and MPN-patients’ care, stands up and not tells the truth.

Dr. Richard Silver and I and others have during the years delivered a large number of papers – studies and reviews – documenting that interferon is not ” an experimental drug” to be used only in selected cases. Interferon is an old horse in the circus which – for unknown reasons – has been neglected, dismissed and thrown away.

In some of his papers – even educational papers in Am J Hematol – Tefferi has mentioned IFN as an inferior agent to hydroxyurea and not to be used in ET, PV or  myelofibrosis. I cannot dissect or understand the reasons for his anti-IFN attitude. When Tefferi now and then in the reference list cites IFN it is often a citation of his own “Letter to The Editor in Blood” reporting on 11 patients with advanced myelofibrosis achieving no benefit of IFN and not tolerating IFN very well due to too high a dosage. From this data Tefferi obviously has concluded that IFN is not a drug of choice for MPN patients while he totally neglects all the data on IFN in the literature, showing that it is working very well and is benefical for the large proportion of patients with MPNs, including  patients with hyperproliferative myelofibrosis as well – shown in studies by Silver and Kiladjian.

Thus, true opinion leaders on the use of IFNs in MPNs are relatively few in the world  and can independently tell quite another story on IFN in MPNs – Richard Silver as the very first, Heinz Gisslinger from Austria and Jean-Jacques Kiladjian from Paris and – of course – not to forget – my colleagues in Sweden and Norway. These colleagues have a huge experience – as do I – in the use of IFNs in MPNs – at least 20 years and we have treated hundreds of patients with IFN during these years.

Accordingly, we have been thus privileged to have experienced:

  • Low dose IFN normalizes peripheral blood counts within a few months in the large majority of patients with ET, PV and hyperproliferative MF.
  • Low dose IFN decreases the need for phlebotomies in the large majority of PV patients within the first 6-12 months but still some patients need phlebotomies in the second ( and third) year.
  • Low dose IFN is well tolerated by the large majority of patients (10-20 % do not tolerate IFN very well – a challenge and a research project why it is so. Soon a study will be launched in Denmark offering IFN-intolerant patients combination therapy with Jakafi .  The rationales for this combination therapy  are described in my most recent paper in Expert Reviews Hematol 2014.
  • Low dose IFN is able to induce regression of myelofibrosis in a subset of patients with hyperproliferative myelofibrosis ( Silver RT et al Blood, June, 2011 ; Kiladjians group in Br J Haematol 2013 ).
  • Low dose IFN induces deep molecular remissions as assessed by the JAK2V617F alelle burden and normalisation of the bone marrow – being sustained even after discontinuation of IFN for up to 5 years (published by the Danish MPN-group  in Ann Hematol and in Hematology ).
  • Low dose IFN – according to the above findings – is the only agent having the potential to induce “minimal residual disease ” / ” operational cure ” in MPNs.
  • Low dose IFN has been shown also to reduce the hard end points – thrombosis and hemorrhage – as compared to historical controls.
  • Low dose IFN is : Pegasys 45 ug x 1 subcutaneously (sc)  per week equivalent to PegIntron 30 ug x 1 sc /week.


  • In 2014  IFN is not an experimental drug in MPNs.
  • In 2014 we have about 25 years experience with the use of IFN in the treatment of MPNs
  • In 2014 we have only one agent – interferon – which has the capability to revert disease progression by inducing minimal residual disease with normalization of the bone marrow in a subset of patients with PV – even being sustained for years without treatment and –  in addition – having the potential to revert bone marrow fibrosis
  • In 2014 we  put great efforts in combatting advanced myelofibrosis, which is characterized by multiple genomic alterations being built up during clonal evolution from the early stages of this cancer – ET and PV. Most lately, telomerase inhibition with Imetelstat has been shown to revert myelofibrosis, but not without significant side effects and the sustained beneficial impact has to be  confirmed in larger series of patients. Our concern about this drug has been reinforced by the FDA halt in clinical trials due to toxicity.
  • In 2014 MPN authorities do not recommend treatment of MPNs at the earliest cancer stage – ET and PV , despite a huge amount of data showing that these early cancers – as all other cancers – will steadily evolve with increasing genomic instability, subclone formation , resistance to treatment and ultimately leukemic transformation in some patients.
  • In 2014 MPN authorities do not recommend to treat MPNs with IFN at their earliest cancer stage – ET and PV – despite a huge amount of data showing that only this agent with no alternatives has the potential to revert the disease process as evidenced by induction of deep molecular remissions and – in a subset of PV patients – normalisation of the bone marrow which is even sustained after cessation of treatment for up to 5 years. 
  • In 2014 we have to discuss and consider if it is still ethical not to offer MPN patients the best available therapy – IFN – at the earliest cancer  stage where the chance of a successful outcome is likely the very best at any time. In this regard MPNs are not different from any other cancer.
  • In 2014 we know that the beneficial IFN effects include among others immune enhancing effects with “restoration of defective tumor immune surveillance ” – of “defective radar surveillance”  and – in addition – telomerase inhibition, which has been shown to revert the advanced myelofibrosis stage but not without side effects and without the long term experience which we have with IFN in MPNs.
  • In 2014 IFN should accordingly be considered as upfront treatment in all newly diagnosed patients with ET, PV and hyperproliferative myelofibrosis, the aim being to treat a cancer from the very beginning to prohibit cancer progression from early cancer stage (ET/PV ) to the advanced cancer stage – myelofibrosis – when immature cells -including stem cells ( CD34+ cells ) egress from the burning hell ( the bone marrow niches – “the chicks flying prematurely from their the nests” – ) to the circulation to seed ( metastasis ) in the spleen, the liver and elsewhere .

In 2014 the world is divided in two – the one having access to IFN and the one not having access to IFN.

  • In 2014 in the world having access to IFN  most patients have the advantage of being treated with IFN with the likely outcome that their counts steadily decline within weeks or months and in the JAK2V617F positive patients with a decline in the JAK2-allele burden as well.

This is fortunate, since the JAK2V617F allele is a thrombosis promoter per se and – according to some epidemiological studies – a tumor promoter as well. Furthermore, the JAK2V617F allele burden induces increasing genomic instability predisposing to additional mutations , subclone formation , resistance to treatment and utimately leukemic and myelofibrotic transformation. To this end the JAK2V617F allele has most recently been shown to induce the generation of reactive oxygen species (ROS) ( Marty et al Leukemia 2013 ), which also induces genomic instability etc. The latter finding is certainly supportive of the viewpoint that the MPNs are “A Human Inflammation Model for Cancer Development,” as most recently described in Leukemia Research .

  • In 2014 in the other world – not having access to IFN – you follow a risk stratification system, allowing patients with low risk MPN -< 60 years , no prior thrombosis, platelets < 1500 units  – to be followed without any cytoreductive therapy but only being treated with aspirin and in PV phlebotomies as well. When are these patients then candidates for cytoreductive therapy ?  They are so, when they succumb to the catastrophe – the thrombosis event or the major hemorrhage, potentially debilitating the patient the rest of his/her life. Then , in most non-IFN-access centers – these patients are treated with hydroxyurea – a potentially leukemogenic agent when being used for long periods – 10 % risk of acute myeloid leukemia (AML) /myelodysplasia (MDS) after about 10 years, 15 % after about 15 years and 20 % after about 20 years.
  • In 2014 –  for all these reasons – we should treat our MPN cancer patients when the cancer is diagnosed and not adhere to “The Wait and Watch Strategy ” but instead follow “The Early Intervention Concept with Interferon” to combat MPN cancer as early as possible and prohibit cancer progression. This concept is also increasingly prevailing in Central Europe where some authorities also abandon hydroxyurea and even believe based on supporting data that hydroxyurea may not only elicit AML /MDS but solid tumors as well. This makes sense when realising that hydroxyurea impairs DNA repair mechanisms and tumor suppressor function (p53) as well.
  • In 2014 it is very exhausting and distressing for MPN-patients that the “Hematological Scientific Community” will not uniformly take notice of the vast amount of convincing data showing that IFN is a highly potent agent which has changed the lives of hundreds of MPN-patients worlwide – even inducing minimal residual disease .

In this perspective – what are we waiting for ? – In my opinion far too many patients have been put on the waiting list according to “Wait and Watch Strategy” and suffer the catastrophe before being treated for their cancer.

We have to rethink the academic approach that we should search the highest level of evidence – the results from a randomised trial comparing hydroxyurea to interferon in high risk patients (The MPN-Consortium Study). In the meantime, our MPN patients will suffer. I think that the time is ripe to reconsider /rethink if the approach – “Wait and Watch ” – is indeed ethical when we know for sure that a substantial proportion of our MPN patients during the course of the disease will suffer thrombotic /hemorrhagic events. Without IFN treatment we know, that the cancer – as all other cancers –  will steadily  evolve along the inevitable path from early cancer stage (ET/PV) to the advanced cancer stage – myelofibrosis – when there is no way back for most patients.

Instead, we should all put our efforts together to break down the barriers between the two worlds – to fuse our concepts on IFN as the cornerstone in today and tomorrow’s treatment of MPNs – likely in the future in combination with statins and JAK2-inhibitors or other targeting agents displaying a synergism with IFN.

Obviously, this pathway is much more fruitful and will undoubtedly open new horizons for our patients instead of being locked as victims by stringent and opposing opinions between MPN authorities.This pathway – the fusion of the two worlds and without barriers between them –  will benefit our patients and – I am convinced – will greatly enlighten the horizon, improve their quality of life and hopefully, also for a large proportion of patients, revert disease progression to a minimal residual disease state.

To  finish – my viewpoint on IFN and on the randomised MPN Consortium Trial

For those of us confident in interferon and having decades of experience with interferon,  I need to cite a lovely US patient who visited me a few months ago in Roskilde for my advice on IFN. “This interferon is really working for me! You saved my life I think. I am very grateful and we now just need to convince the rest of the world of the need for early treatment. I am out there singing from our hymn sheet but it is amazing to me how often the world is skeptical of the obvious. As you said to me once, I remember it well, “I do not need to throw a coin on the ground 100 times to prove that will not bounce off the ground and back into my hand”

Best wishes and good night from Copenhagen


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Comments on the Open Letter by Dr. Richard T. Silver

Richard Silver MDZhen has asked me to make some editorial comments regarding the passionate, from the heart exposition regarding the use of interferon by Professor Hans Hasselbalch.  I agree with everything he says!

In summary, I would emphasize the following:

Recombinant interferon (rIFNα) is the only drug used in the myeloproliferative diseases that has a physiological basis for its use.  In addition to affecting abnormal megakaryocytopoiesis, presumably the cause of the fibrosis, it has been shown by Dr. Ann Mullally from Harvard (published in Blood) that interferon specifically affects PV stem cells.  Thus, we have a physiological basis for its use instead of the non-specific killing activity of hydroxyurea and other similar compounds.  We tend also to forget that besides the leukemogenic potential of hydroxyurea emphasized in a recent paper by Professor Kiladjian in France, it has many other side effects which our readers may have developed, including mucositis, painful ankle ulcers, and other abnormalities of liver and kidney function.

It should also be recognized that those individuals who favour the use of hydroxyurea, especially our colleagues in Italy, do not have access to interferon. They favour the use of hydrea as do I when its use is necessary, compared to other chemotherapeutic drugs such as chlorambucil, which are certainly more leukemogenic.  There have been no comparative studies comparing hydroxyurea to busulfan in the MPNs, but many of you know that I use low dose busulfan (as does Dr. Tefferi) in some elderly patients in whom we do not wish to use interferon.  In fact, Dr. Emil Kuriakose and I recently reported its use in “advanced” polycythemia with good changes in JAK2 allele burden!

For years prior to meeting Dr. Hasselbalch professionally, who has become a good friend as well as a good colleague, I decried, as did he, the “watch and wait” attitude recommended by some of our colleagues.  It is important to remember that in medicine, as in history, those who forget the past are doomed to repeat it.  More than 30 years ago, Dr. Najean, the French famous haematologist and an expert in treating PV, said that it was impossible to maintain a patient on phlebotomy only, that the production of significant iron deficiency with its attending side effects would invariably occur (which it does) and that the disease progresses unchecked, which it does.

We at Cornell rarely if ever see our patients with polycythemia treated with rIFNα with large spleens and fibrosis of the bone marrow if in fact they have been treated with interferon early in the course of the disease, which is our policy.  An argument can be made for observation only for those who present with a so-called “myeloproliferative disorder” that is not associated with an increased red blood cell count, so-called “pre-PV” but we have had patients now who insist on being treated “early” in their illness so as not to have it progress.  This is consistent with our ideas in other forms of cancer, such as “prophylactic mastectomy” in women at high risk for breast cancer, as just one example.  In ET, I am against the “watch and wait” attitude for a catastrophic event to occur while patients are being treated as a “low risk patient” only to become a “high risk patient” when a terrible thrombotic event occurs.

In primary myelofibrosis, we do not like to see the disease progress.  It is for this reason that we now have an investigator-initiated trial in early myelofibrosis to see whether or not we can prevent the progression of myelofibrosis with early treatment rIFNα rather than waiting for the disease to progress and then use JAK2 inhibitors such as Jakafi.  The combination of interferon plus Jakafi, as Hans is using it,  is a wonderful trial.  It makes a great deal of sense.  Unfortunately, for a variety of reasons, we cannot launch this type of study in the US, although I have wanted to do so for several years.

In summary, I agree with Hans’ viewpoint; fortunately I am not as pessimistic as he, since now we are seeing more and more patients using interferon and I have not had any experience where an insurance company has not permitted its use.

I hope his article and my commentary are helpful to our MPN patients for whom we are dedicated to serve.





Take me back to the Contents

© Dr. Hans Hasselbalch, Dr. Richard Silver and, 2014. Unauthorized use and/or duplication of this material without express and written permission is prohibited. Excerpts and links may be used, provided that full and clear credit is given to with appropriate and specific direction to the original content.


Comments on: "Response to attacks on interferon — An open letter" (22)

  1. Dante Romano Neto said:

    As a 59 years old ET patient, I find this, very important information, and on time.
    Thank you for sharing.

  2. Michelle Palmer said:

    Many thanks for the above research and forward thinking commentary.
    Is it possible to get an update of current research please. Also can Interferon be safely used before, during and after pregnancy? I am in Australia with a daughter who has ET and PV who is hoping to become pregnant asap. Many thanks. Michelle

  3. Charles R Williams said:

    I developed an ankle ulcer after 4 years on HU. I have had 2 injections of IFN after going off of HU for 10 weeks. Well tolerated. Took my platelets from 850 to 550 to 500. I am lucky to have a hematologist at Moffitt willing to prescribe IFN.

  4. Kathy Van Meter said:

    It saddens me that all who need it cannot have access to inf. Knowledge is power and we owe it to ourselves and those who come after us to advocate the use of drugs that will give all a fighting chance. Peace…………

  5. Jeremy Smith said:

    Mike we are all the same boat regarding the 180MCG issue versus what we actually take. Some MPN patients save the produce and use it later. I was told by Dr. Silvers office never to do this that the product is never to be used this way and the quality of the product is impaired when patient do this.

    • Mike Carter said:

      If Pegasys is pre-packaged in syringes which contain just 0.5ml of carrier liquid (with the active 180mcg ingredient not necessarily uniformly mixed), then it must be very hard to determine whether you’ve taken the desired 45mcg “low dose” treatment each week. There’s an assumption in the research papers (and in Dr. Hasselbalch’s open letter) that this is not an obstacle. I’m trying to understand why not (and hoping the answer will also somehow help reduce cost!). I’m persuaded that interferon treatment is a rational thing to attempt, but definitely want the low-dose version. In terms of Dr. Hasselbalch’s obvious (and justified) frustration, I’d identify the packaging of the desired dose as a bigger issue than the ignorance of some doctors about this treatment option.

      • hi Mike! Pegasys 180mcg is as well as 135mcg (which i am lucky to be able to use against PV Progression) is a Depot – Treatment. so you do not have to apply it weekly. i started off weekly with it, reducing two every two and now as well every three weeks. i think i am really lucky to be able to receive the best Treatment available – even if it was a bit of a struggle first…i now really do think it was worth it!!! all the best to you!

  6. Mike Carter said:

    I’ve found a hematologist at Princess Margaret Hospital in Toronto (Ontario) who’s open to prescribing interferon to help treat my PV. But at least in Ontario, Roche sells interferon only in 180 microgram single-use doses for hepatitis treatment. How do others handle that, when we only need 45 microgram doses for PV treatment? Interferon is far too expensive to just throw away three quarters of every pre-packaged dose. This is not about being frugal, it’s about being able to afford interferon or not. If I can’t afford interferon then I’ll have to stick with phlebotomies every 4 weeks, and that’s not a good thing (they’re not reducing my platelet count or my continually-increasing white blood cell count).

    • Bryan Cronk said:

      Hello Mike Carter, my wife Linda is Post ET – Myelofibrosis and we have been denied Interferon / Pegasys by two doctors at Princess Margaret Hospital. It would be appreciated if you would share the name of the Hematologist at Princess Margaret who is willing to prescribe Interferon to MPN patients. You can let me know at if you do not want it to go public on

      The Medication Reimbursement Specialists at Princess Margaret may be help you with the cost coverage for your Interferon / Pegasys. They are fantastic and can be reached at 416-946-4501 Ext. 5129 They may be able to help with alternative suppliers and packaging formats as well?

      Best wishes for your treatment on Interferon, Bryan Cronk

  7. Very interesting as research is.

  8. Jamie Strause said:

    Zhen: thank you for getting the experts to speak about interferon. Their years of experience and enthusiasm about it confirm for me that it is the right treatment decision.

  9. Jeremy Smith said:

    Emily, excellent questions. Not sure if you read my article on INFN but I had to fight for INFN and I think in situations where Doctors have bias you have to demand it and fight for it. Otherwise you go see someone like Dr. Silver or Dr. Mesa and they can prescribe it for you and work with your local hematologists.

  10. Rochelle Moore said:

    “The combination of interferon plus Jakafi, as Hans is using it, is a wonderful trial. It makes a great deal of sense. Unfortunately, for a variety of reasons, we cannot launch this type of study in the US, although I have wanted to do so for several years.”

    I am wondering what these “variety of reasons” are? This combination does seem like it could be beneficial. Taking both meds at a lower dose would likely decrease side effects, and it may be that they work synergistically for an increased beneficial response from each.

  11. I really appreciate both the publisher and the doctors for this very passionate expression of advocacy on our behalf. I would really like to see responses by other specialists such as Drs. Mesa, Verdostock, Stein etc on interferon, especially for MF, as opposed to PV and ET. Do they agree that Pegasys should be the “go to” drug for most MPN patients? If not.. why not? If yes… then how does this message get out to the doctors who treat us? That use is off-label.. many doctors won’t willingly use a drug off-label unless that use has really become mainstream (or widely recognized among specialists). Most of us, I suspect, are NOT treated by MPN specialists on a regular basis, but are only able to consult with one periodically. How does a use that is currently off-label become ON-label, and can Drs H and S push for this to happen? I’d love to read comments from any of the members here

  12. Howard aselinger MD said:

    My personal experience , published in the American Journal of hematology, with interferon providing dramatic benefits for both polycythemia vera and chronic lymphocytic leukemia in the same patient.

  13. Bonnie Evans said:

    Brilliant article that will help thousands make an intelligent decision. I love how the facts were spelled out.

  14. Jeremy Smith said:

    Dr. Silver thank you for speaking up. You were the reason I switched to INFN in spite of my Doctors and hearing Dr. Tefferi telling me not to. Just wish I had done so when I had PV and not MF but happy to be on INFN.

  15. Dr. Hans Hasselbalch’s many contributions and great effort in fighting for the MPN patients are much appreciated. I really enjoyed reading his papers. Those papers made a great difference!

  16. gunther rehberger said:

    Thank you to the MPN forum monthly for posting the open letter on INF. Well overdue that someone deals with the negativity surrounding INF. Well done!
    Gunther Rehberger

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