[00:14:52]

Soundings: Understanding and Identifying Refractory CMV Infections in Transplant Settings 

All right. So I'm going to talk about identifying and understanding refractory CMV infections in transplant settings.

[00:20:48]

          CMV: The Most Common Infection After SOT  

So as you know, CMV is the most common infection after solid organ transplantation. After primary infection, CMV is usually latent in humans unless they are immunosuppressed or pregnant. Roughly half of all adults in many European countries, the US and Canada, Australia about 50 - of all of those adults, about 50% are CMV positive.

It is higher in other regions. So if you're practicing in Brazil or Italy or India, there are higher rates of positivity in CMV - for CMV IgG positive adults.

There are good but not perfect options for prevention and treatment after transplant. And as you know, it causes a spectrum of disease. Resistant/refractory disease adds complexity. And I think that's why many of you are here today and really adds a burden to what we - how we manage these patients.

[00:21:43]

          Direct Effects of CMV and the Continuum of Infection  

So there are the direct effects of CMV, which is really, you know, what infection looks like. And that ranges from asymptomatic CMV to CMV syndrome, which includes fever and malaise, all the way to CMV disease where there's gastrointestinal disease, pneumonitis, etc..

And all of these are affected by the things that you can see listed underneath. So we can significantly decrease rates of direct CMV, the direct effects or significantly decreased rates of CMV infection through preemptive therapy and monitoring antiviral prophylaxis if there's prior immunity, CMV immunoglobulins, vaccines, monoclonal antibodies and cellular therapies, or all things that are in development.

And then the more immunocompromised they are, the - or if prophylaxis has ended, or if they have de novo, or what we sometimes call community exposure, those can all be unexpected areas where we see higher rates of CMV - or not necessarily unexpected, but higher rates of CMV.

[00:22:44]

Indirect Effects of CMV (Organ Transplant)  

And then there the - the - the kind of evil specter of the indirect effects of CMV where we see higher rates of all types of infection, higher rates of PTLD, higher rates of cardiovascular events, new-onset diabetes after transplant, immunosenescence is altered, acute rejection and mortality occur at higher rates. In other words, CMV is bad, right?

So - and then there are indirect effects on the individual organs, as you can see listed there on the right-hand side of the slide. We often think that if you really want to enhance outcomes for your individual patient as well as your overall program, the best way to do it is to really prevent CMV as best you can.

[00:23:24]

          Impact of Prior Immunity: Patient-level Depiction of the Magnitude of Viral Load and Duration of Viremia in D+R- vs D+R+

There's some really interesting data that was just recently published from British Columbia, and they looked at the impact of prior immunity. The slide on the left is the D+, the donor-positive recipient negative group, and the slide on the right is when the donor and recipient are both positive. And I thought that the magnitude and duration of the viral load you can see here D+/R+ plus on the right. You know, it's like not really that bad, right? Not such a high magnitude of CMV. And in general it's cleared and whatnot. So probably lower indirect effects.

But the slide on the left you can see it's really pretty - pretty significant magnitude and duration of CMV. That's a brilliant paper if anyone wants to read about CMV kinetics.

[00:24:08]

          Treatment of CMV After Transplant  

So treatment of CMV after transplant is overall pretty straightforward until - and I just had the - we just published the fourth international guidelines on CMV management. And so this is adapted from that. You know, the first step is determining the severity of infection. And for the vast majority of people, it's fine to give - if they have mild to moderate CMV to treat them with oral valganciclovir, renally adjusted dosing. That's pretty straightforward. I would say that's 90% of what I do is oral valganciclovir treatment as an outpatient.

But for people with severe CMV infection, ophthalmological disease, you know, retinitis, colitis, if there's severe GI malabsorption concerns, or if there's resistant/refractory disease, so sight threatening, life-threatening disease, I usually admit them to hospital also if they have a DNAemia over - somewhere over 100,000 IU per ml, I usually admit to hospital for intravenous ganciclovir.

And then for almost everybody it's a time to think about could they be on lower immunosuppression? Do they have hypogammaglobulinemia? Do they need their immunoglobulins replace that type of thing.

[00:25:21]

          Treatment of CMV After Transplant  

The treatment of CMV after transplant also includes, so checking a weekly CMV DNAemia on plasma or whole blood. And in the guidelines, we said that antiviral treatment should be continued for a minimum of two weeks until clinical resolution of disease and a decrease in CMV DNAemia below the institutional laboratory specific threshold, which was a per grade, a strong and moderate recommendation.

And so this might be below the lower level of quantification on a single sample with a highly sensitive assay or two consecutive weekly samples with less sensitive assays. And one thing that we have both thought a lot about is you don't really have to drive this down to zero, like it's really getting it, say, below a certain institutional threshold that might be below 200 IU per ml. But I see a lot of people who are trying to with a very low, you know, 78 IU per ml, very low numbers, and they're trying to drive it to zero. And that probably is not necessary.

So you don't - you don't have to completely ablate it. You just have to have it very low.

And if - but importantly, if the DNAemia doesn't fall after two to three weeks of appropriately dosed treatment, or if the clinical status isn't improving, then you really start need to - start to think about is this resistant/refractory disease? And do I need to send resistance testing?

There's an important pearl which has been in all of the guidelines. But basically many people, when you start treatment of CMV, they often go up at week one. And so you'll see a DNAemia that can increase at week one. And for me, that's where that concept of DNAemia is helpful because it just means you have potentially more CMV fragments that you're amplifying. So it may increase at week one, but hopefully by week two you should see a significant downward trend.

[00:27:09]

          Difficult-to-treat Resistant/Refractory CMV Risk Factors  

So what are the risk factors for difficult-to-treat or resistant/refractory CMV. So the number one risk factor is when the donor is seropositive and there's a seronegative non-immune recipient. That is the number one risk factor.

Also if there's increased immunosuppression or older transplant recipients who have perhaps no prior CMV immunity or waning herpes virus cellular immunity. Also the use of belatacept. When there's a D+/R- situation and patients are on belatacept, for me, that has been one of the top risk factors for developing very challenging to manage CMV. So I usually say can we get them off the belatacept at least until we can clear the CMV?

Also, people who've had longer exposures to antivirals, or if there's a very high DNAemia at the time of antiviral initiation or during treatment. And then antiviral underdosing or mini dosing is something that we really recommend avoiding, because underdosing of antiviral medications is kind of one of the top ways to breed resistance. So if you're doing, it's really important to know the patient's kidney function and make sure you're accurately dosing.

I think many people end up overdosing valganciclovir. And so then they get some toxicity. So it's important to dose correctly. So not overdose, not underdose. Just hit right on - right on the target. And I actually spend a lot of time talking to my nephrologists about what is this patient's true renal function. And that's often very helpful. And then you often have to keep adjusting for the valganciclovir.

Also it depends which organ is being transplanted. But certainly lung, intestinal and composite tissue transplants have the highest rates of resistant/refractory CMV.

[00:29:00]

          What is the New Definition of Resistant/Refractory CMV?

So what is - there's a new - we had new definitions that were published this past year for resistant/refractory CMV. So refractory CMV infection. So this is like the first step, right? Recognizing that something's not going well. Refractory disease is defined as when their CMV Viremia DNA - DNAemia or antigenemia that increases at least one log in the same blood compartment, or if it just persists. So it stays - either increases a log or stays the same after two weeks of appropriately dosed antiviral therapy. And again, I can't stress how important it is to make sure your antiviral medication is appropriately dosed.

Refractory end organ disease is when there's a worsening in signs and symptoms, or progression to end organ disease, or a lack of improvement in signs and symptoms after at least two weeks of appropriately dosed antiviral therapy.

Usually, we're not seeing so much end organ disease these days. We're more in the usually just infection and just looking at the patients signs and symptoms, but often their DNAemia levels. I will say that these guidelines were specifically developed for clinical trials, but in some ways the thought around them can reflect what we are doing in clinical practice.

[00:30:14]

          What is the New Definition of Resistant/Refractory CMV?

Resistance CMV infection is where they have refractory CMV, so not improving CMV or worsening CMV, plus the presence of a known viral genetic mutation that decreases the susceptibility to one or more anti-CMV medications.

[00:30:27]

          CMV Genotyping for Drug Resistance

So resistance testing. So there are two types of resistance testing out there that are commonly used. How many of you have access - how many of you in the room have access to CMV resistance testing?

Okay. So most people in the room have access to that. So the Sanger sequencing method is what had been used for a long, long time. And this is quite good. It detects variants down to about 20%. So overall very good and accurate but does miss some of them.

Next-generation sequencing can detect mutations at a 5% to 15% variant concentration. So is more - more sensitive than the Sanger method.

We recently, about three years ago switched, from Sanger to NGS by switching different commercial laboratories. So before - before or if you don't have access to CMV genotyping, we recommend following the algorithm that we will be showing you from the guidelines with presumptions as to the best choices to make.

And just be aware that if you're - you need to have a certain DNAemia, usually at least 1000 IU per ml to get good sequencing results. The drug resistance testing is actually quite expensive, somewhere in the range of a few thousand dollars often, so don't send it if it's like, you know, 284 because it's not going to work and you will have spent the money. So I always try to do good stewardship.

[00:31:56]

          Burden of Refractory/Resistant CMV

The burden of refractory/resistant CMV is quite significant. You know, CMV is like pretty easy, except for those few patients with resistant/refractory disease, which I think is why you're all here. And they really can take up a lot of our - a lot of our time. And these patients really suffer.

We think that overall the rates of resistant – refractory/resistant disease are generally quite low, but have reportedly - been reported in somewhere from 2% up to 12%. I think if you do have higher rates of refractory/resistant CMV, you might want to review your protocols.

I do have a lot of people that contact me that are using mini dosing or valganciclovir or too short of prophylaxis or whatnot. So there are areas where sometimes we can tweak things so you have lower rates overall.

These folks have higher rates of hospitalizations, more complex care. They have increased risk of graft loss and rejection, higher rates of morbidity and mortality, and overall increased cost. And Dr. Humar will talk about that. But, you know, the medications, hospitalizations, clinic visits and testing really all add up.

[00:33:02]

          Posttest 1

Okay. So let's do the posttest again. So this is where we're going to discuss the answers. But for a kidney transplant recipient, the earliest you should suspect refractory CMV infection is if there is - I think go ahead and answer this because I've read through it before, but as if there is unchanged or increasing CMV DNAemia after what duration of appropriately dosed antiviral therapy?

1. Two weeks;
2. Four weeks;
3. Six weeks; or
4. None of the above.

So go ahead and answer it, including the people at home. Go ahead. Good. I'm going to show the answer.

[00:33:47]

          Posttest 1: Results

Great. Oh, what good learners, right? You all got an A+. Excellent. Great. Right.

[00:33:57]

          Posttest 1: Rationale  

And so two weeks is the right answer. And refractory CMV is identified by CMV DNAemia that increases or persist after at least two weeks of appropriately dosed antiviral therapy.

[00:34:09]

Charting the Course: Antivirals for Refractory CMV Infections            

Great. And now I'll turn this over for discussion around antivirals.

Dr. Atul Humar (Ajmera Transplant Center): Thank you, Camille, and thank you for attending today. So we're going to take a deeper dive into antivirals, the mechanism of action, when to use them and the data supporting it.

[00:34:27]

          GCV: Mechanism of Action  

So let's start with ganciclovir. Of course the - the backbone of what we use either valganciclovir, which is a prodrug of ganciclovir or ganciclovir, requires mono phosphorylation. And this is done by the viral protein kinase encoded by UL97, and then triphosphorylated by cellular enzymes, and then binds to the dNTP binding site on UL54, which encodes the DNA - viral DNA polymerase.

[00:34:55]

          Ganciclovir and Valganciclovir: CMV Clearance Kinetics  

And as we heard, ganciclovir or valganciclovir are the initial mainstays of therapy. And this trial, the VICTOR study, done now 15 years ago or so, showed that both were really equivalent in the vast majority of patients. And you can see on this graph on the y-axis is the viral load. Back then we’re using copies per ml, and an x axis is time. And you can see oral valganciclovir versus IV ganciclovir were similar in terms of viral clearance kinetics.

Both are highly potent drugs. The most common limiting toxicity is cytopenia. As mentioned before, a really important point, and that was shown in the VICTOR study, is that viral load may actually increase within the first week of treatment. And this is just a dead virus spilling out from the tissue into the plasma or whole blood. And be very careful about interpreting small changes in viral load. Remember, it should be interpreted in a logarithmic scale.

[00:35:59]

          Considerations for Renal Function Monitoring With Ganciclovir and Valganciclovir  

So monitoring of renal function is very important with ganciclovir and assessing renal function. And that's primarily because you have to dose adjust. It's not because - you know, a lot of people will say ganciclovir is nephrotoxic, but it's actually not nephrotoxic in the vast majority of patients. So you have to monitor to dose adjust.

And in the - importantly, in the VICTOR study, the creatinine clearance or the renal function was estimated using the Cockcroft-Gault formula, not eGFR. And if you go to most hospital settings now eGFR is - is more commonly used. But really the - there - there hasn't been the evidence that you can use eGFR to calculate ganciclovir dose. So you just need to be cognizant of the differences in these measurements.

[00:36:46]

          Patient Case #1: CMV Treatment  

So we'll do a case to start with. So 55-year-old women, four months after kidney-pancreas transplant. D – CMV D+/R+ ATG induction and is on standard immunosuppression with Tac, MMF and prednisone. So she receives three months of valganciclovir prophylaxis. A month later, she presents with fever, fatigue, mild diarrhea, myalgias, temperature is 38.2. Creatinine is 1.97 milligrams per deciliter or 174 micromole per liter. And you can see the white count and platelet and hemoglobin are all low. The CMV viral load is 14,000 IU per ml.

[00:37:33]

          CMV Treatment Recommendations  

Now, the treatment recommendation in her would be to start either oral or IV ganciclovir. So we would typically choose oral valganciclovir for her, unless we were really concerned about absorption with the diarrhea that she's having. Monitor the viral load weakly, monitor CBC, creatinine and treat as - as Dr. Kotton pointed out, treat until you reach a certain threshold. So it doesn't necessarily have to be negative as undetectable, it has to be below your center specific threshold that you define.

And then after treatment, you can monitor patients or you can give secondary prophylaxis if you believe they're at high risk for recurrence.

[00:38:14]

          Patient Case #1: 2 Wk Later

So let's say this patient receives, you know, valganciclovir or ganciclovir for two weeks, but she remains clinically unwell. And now the viral load has gone from 14,000 to 44,000. So you send for resistance testing, you reduce the immunosuppression.

[00:38:33]

          Poll 4

And the question is what do you do next? So the - so answer this question. So

1. You could increase the ganciclovir dose to up to a maximum of 10 milligrams per kilogram BID, adjusted for her renal function. So this would be double dose ganciclovir;
2. You could change to IV foscarnet; or
3. You could change to oral maribavir.

Okay. Two of them. First. Yeah. Okay. So that’s interesting. So the majority of people would actually double the dose, ganciclovir adjusted for renal function. This - we'll discuss this in more detail. There's not necessarily a right or wrong answer to this question.

[00:39:29]

          Antiviral Drugs for CMV: Mechanism of Action  

So let's go through the - the mechanism of action of the alternative antivirals, starting with - we already discussed ganciclovir, and that's shown in the - in the blue here, binding to the dNTP binding site.

Cidofovir does not require that initial phosphorylation step. So it just requires a triphosphorylation by cellular enzymes. And then it also binds to the dNTP binding site on the UL54.

Foscarnet on the other hand does not require any phosphorylation, it directly binds to UL54 at an alternative site called the pyrophosphate binding site. So you can see how the resistance can arise for each of these drugs. For ganciclovir, it’s a mutation in UL97 so that it no longer phosphorylates ganciclovir, or a mutation in UL54 so that it no longer binds ganciclovir.

And cidofovir, you require a UL54 mutation. And foscarnet, you require a UL54 mutation for resistance.

[00:40:29]

          Foscarnet and Cidofovir for CMV Treatment

So what about foscarnet and cidofovir? Well, historically, foscarnet has been the primary alternative therapy for refractory/resistant CMV. And it's interesting because, you know, people have a lot of experience with foscarnet, but there's no actual large randomized controlled trial of foscarnet in solid organ transplant recipients. And there's a number of case series. This is one of the larger ones that looked at 22 patient - solid organ transplant patients receiving foscarnet and they had a high rate of toxicity.

The - the actual inhibition of viral replication was quite good. It's a very potent drug. But there's a very high rate, especially in solid organ transplant patients of nephrotoxicity. Other adverse events might include electrolyte abnormalities, GI disturbance, and cytopenias.

Cidofovir, there's actually even less data in solid organ transplant patients. And I think most of us would very, very uncommonly or rarely use cidofovir. But this is one of the larger studies. It's 16 patients of whom 10 were solid organ transplant patients. The rate of nephrotoxicity was very high, 37%. And there was also a high rate of ocular toxicity, so uveitis. And 50% actually had failure to clear DNAemia.

[00:41:56]

          Maribavir for CMV Treatment  

Now the other more recently licensed drug for treatment of refractory/resistant CMV is maribavir. It's an oral drug only, so there's no IV maribavir. And the way this drug works is actually inhibits the viral protein kinase UL97. So this is also the protein that phosphorylates ganciclovir. But in the virus it seems to have another function. It seems to be involved in nuclear egress of the virus. So when the viral particle is made in the nucleus, it has to egress out of the nucleus into the cytoplasm of the cell, and blocking UL97 seems to prevent that process.

Maribavir does not affect the UL54 polymerase. The good thing about maribavir is it's not myelosuppressive or nephrotoxic. The main side effect is a taste disturbance or dysgeusia. So you actually have to warn patients about that before starting the drug so that they're aware that that might happen.

[00:42:56]

          SOLSTICE: Maribavir vs Investigator-Assigned Therapy for Resistant or Refractory CMV

This is the phase III trial that led to approval of maribavir for this indication. So it's called the SOLSTICE study, and it included both stem cell and solid organ transplant patients with a viral load or DNAemia above 910 IU per ml, and they were deemed to be refractory/resistant by the investigator.

Patients were randomized to 400 milligrams PO BID of maribavir for eight weeks or what was called investigator-assigned therapy, which meant that it was the choice of the investigator what drug to give. And if we look at what drug those patients got, most of them got either ganciclovir, valganciclovir often at a higher dose, or foscarnet were the two most common options.

In that arm, they were allowed to also rescue with maribavir if the investigator felt they were failing or intolerant of the IAT. The primary endpoint was clearance of CMV at week eight. I want to emphasize that the - at the - the bottom line here at the - if you look at the viral loads in those patients, they're - they’re actually quite low. So the median viral load was 3,377 and 70% of patients had CMV DNAemia levels of less than 10,000 IU per ml.

[00:44:18]

          SOLSTICE: Symptom Control and Confirmed CMV Viremia Clearance  

This is the results of the study. So the - the maribavir was superior to the IAT. And we can see at week eight. So remember it's eight weeks of therapy. The clearance was 55% in the maribavir arm versus 23.9% in the IAT arm. After patients stopped therapy, then they were - there was recurrence of DNAemia. And you can see by week 12 it's 22% - 22.6 and 10.3%. And by week 20, it's 18.3% and 9.4%.

There were a lot more patients in the IAT arm who did not complete their therapy, so they had to stop typically due to neutropenia or leukopenia in the ganciclovir patients or due to nephrotoxicity in the foscarnet patients.

[00:45:09]

          Maribavir Resistance Maps to UL97

Now, one of the main concerns with maribavir is the development of resistance. And there was this study looked in detail at all those patients enrolled in the SOLSTICE study. And what they found was that maribavir resistance developed in 26% of those patients. So this is emergent resistance means it's developing after initiation of the maribavir.

And where does maribavir resistance map to? It maps also to UL97, just like ganciclovir resistance does. But the resistance mutation sites tend to be different for the most part. The three most common maribavir resistance mutations here are shown in blue, and only one of those has an overlapping ganciclovir resistance, which is the C480F mutation.

In the SOLSTICE study, the median time to development of maribavir resistance was about 56 days after starting treatment.

Now the clinical clue how do you suspect maribavir resistance is, if you have a patient on maribavir and the viral load starts to go down, and then while they're still on the drug, the viral load starts to go up. About 86% of those patients will have maribavir resistance.

[00:46:26]

          Pearls From the International CMV Guidelines  

So here's the - the pearls from the international guidelines. So what we said is refractory CMV without detected resistance should be managed by monitoring patients’ current treatment or switching to another therapy depending on viral load trajectory, clinical conditions, AEs, availability and cost.

We said maribavir is the principal alternative therapy for treating patients with CMV that is resistant to ganciclovir or foscarnet, and that was a strong recommendation. And then we said foscarnet is the initial therapy for clinically unwell patients with high viral loads. And this was a weak recommendation. But based on a lot of discussion and a lot of opinion from the group, we - we put out a cut - a cutoff of approximately 50,000 IU in plasma based on expert opinion.

[00:47:23]

          Algorithm for the Treatment of R/R CMV Disease  

This is a - there's a very nice algorithm within the guidelines which Camille will present. This is a simplified version of the algorithm. But you can see if you have inadequate response to treatment, check drug dose, reduce immunosuppression, send for resistance testing.

If you have a refractory/resistant CMV, at that point, you look at what the viral load is. Is it low to moderate or is it high? If it's low to moderate, you can give maribavir. If it's high, you start with foscarnet, especially if the patient is clinically unwell.

And then you can step down to maribavir once you have good viral control. If you have CNS disease or retinitis, you should avoid maribavir in that setting because the absorption concerns and it hasn't been well studied.

If you have a proven resistance, then you choose the antiviral based on the resistance profile, whether that could be maribavir or foscarnet.

[00:48:25]

          Costs of Maribavir vs Investigator-Assigned Therapy for Refractory CMV Post Transplant  

Now one of the issues with maribavir is that it is very costly. And this was a follow up study to the SOLSTICE that looked at the cost analysis of patients enrolled in that study. So the first column is maribavir. The second column is investigator-assigned therapy. So they looked at treatment costs. They looked at costs with re-treatment, so patients who relapsed. They looked at hospitalization costs. They looked at costs due to adverse events. And they looked at total organ graft dysfunction and loss and the costs related to that.

And in the end, the two costs are actually pretty similar, with maribavir being just slightly cheaper than the investigator-assigned therapy when you take all those costs into account.

[00:49:14]

          Guideline Recommendations: Additional Therapies for Resistant/Refractory CMV  

So here are some additional kind of pearls from the guidelines. We had a lot of discussion on the use of adjunctive IVIg or CMV IgG. It's not routinely recommended but might be considered for refractory/resistant CMV and very severe CMV.

T-cell therapy, there's a big section on T-cell therapy in the guidelines, and it does seem to work in a subset of patients, but the trials are very small. Many - many of the products out there are typically third party T-cell products are not routinely available in many jurisdictions, but there are other trials going on, and this is an option for selected patients.

Several drugs used for other purposes, including mTOR inhibitors like sirolimus and everolimus, leflunomide and artesunate are reported to have anti-CMV effects. But really, we didn't feel that there was sufficient evidence to recommend any of these drugs for treatment of resistant CMV infection. And that really, if you're using an unapproved or experimental therapy, the evidence is weak and limited to anecdotal reports, and it should be done in the context of a clinical trial.

[00:50:28]

          Can I Use Letermovir for CMV Treatment?

Now one common question that we get is can we - can I use letermovir for treatment? And - and I think this was especially before maribavir became widely available. This was actually commonly being done in practice. And so how does letermovir work? Well, when the virus is replicating, it produces these concatemeric strands of DNA which are adjoining strands of DNA. And those require cleavage prior to packaging. And that cleavage is done by the terminase complex, which is a set of proteins that combines together.

And one of those proteins is encoded by UL56, which is inhibited by letermovir.

[00:51:12]

          Letermovir for CMV in Transplant Recipients  

So what's the data on using letermovir for treatment? There's not a lot of data. Most of its case series. This is one of the larger case series. There was 47 transplant patients including both stem cell and solid organ transplant patients. 37 of those had a viral load of less than 1,000 and 10 had a viral load of greater than 1,000.

What the authors saw in this study was that those with a viral load less than a 1,000 seemed to have a reasonable response, although we don't know how many of those would have cleared viremia on their own.

But those were the viral load greater than 10,000 had really kind of mixed outcomes, with a lot of failures and development of letermovir resistance. So in the guidelines, what we recommend is against the routine use of letermovir for treatment due to potential for resistance emergence, especially if the viral load is - is reasonably moderately higher or very high.

[00:52:09]

          What About Combination Therapy?

Now the other question that arises a lot is combination therapy. And really this is a data free zone. It's a clinical anecdotes only, case reports. And data are needed on the use of combination therapy, although many experts might use them - might use it in selected situations. Kind of the cost of these and the access to them can become significant issues.

Now here are some of the theoretical combinations that could be considered. In the past, many people used to use ganciclovir plus foscarnet to try to spare the foscarnet doses, but there is minimum evidence to support this and it's not really recommended anymore.

You could add letermovir to either ganciclovir or to foscarnet or to maribavir. There is a theoretical benefit to targeting two different viral enzymes, targeting both the UL54 and the UL56. But - but again, there is no - no data yet to support doing this.

You could add - add foscarnet to maribavir, but what you should not do is add ganciclovir and maribavir. And the reason for this is the two appear to be antagonistic. And that makes sense because the maribavir will inhibit UL97 and so it won't phosphorylate ganciclovir anymore.

You can add CMV immune globulin, and many experts reported adding either CMV-IG or IV-IG for severe disease or refractory/resistant CMV.

Many in the room, at the time we did, the expert panel preferred using CMV-IG in that setting. There are other agents being investigated, but these are best done through clinical trials.

[00:53:56]

A Deep Dive Into Complex Clinical Scenarios Involving Refractory CMV Infections 

So with that, I thank you. And now what we'll do is we'll dive into some complex and interesting cases.

Dr. Kotton: Awesome job. Okay, great. So now is the hard part. You've taken in all the learning. And these are cases that we - we bring from our experience.

[00:54:14]

          Patient Case #2

The first case is a 64-year-old woman who had thin basement membrane disease, who underwent kidney transplant from a deceased donor, donor-positive/recipient-negative for CMV, of course.

The surgery was complicated by thrombotic microangiopathy from tacrolimus. So she was converted to belatacept/prednisone and azathioprine. And she didn't tolerate mycophenolate either.

She was on - so already you're kind of thinking oh, D plus or minus belatacept, okay. So six months of valganciclovir as per institutional protocol. And one month after the valganciclovir prophylaxis ended, she was on surveillance after prophylaxis. So we were - we knew that this was a high risk situation. So we were monitoring her weekly. She developed CMV.

And as you can see there, her initial CMV DNAemia was just over 10,000 IU per ml. She was started on valganciclovir treatment at 450 milligrams twice a day. Week one, her DNAemia went from 10,000 up to 22,000. You know, it's not even half a log difference, but still it's - goes up at one week. Just like I said, commonly happens. No drama.

By the second week, she's down to 17,000. Okay. Kind of wish it was a little lower than that, but nonetheless - you know, anyway. And the following week, she's down to 1,677. So great. Then 261 and then undetectable. And we switch her to prophylaxis.

Okay. So like a pretty good story overall, although you are kind of thinking, well, D plus or minus and belatacept and she's presenting this case, right?

[00:55:50]

          Poll 5

So she's on prophylaxis. And while on prophylaxis, she has breakthrough CMV DNAemia at 18,000 IU per ml on plasma. So what would you - what would everyone in the room do and everyone online, what would you do at this point? Would you:

1. Start maribavir;
2. Start foscarnet;
3. Start letermovir;
4. Start higher dose valganciclovir treatment;
5. Start intravenous ganciclovir treatment; or
6. Would you wait for resistance testing to return in like one to two weeks.

So go ahead and vote, and let us know what you would do.

[00:56:41]

          Poll 5: Results  

Okay, great. So the majority - the most common answer was start higher dose valganciclovir treatment. The next one would be start maribavir at about a third of people, and then a little bit would switch to intravenous ganciclovir or wait for resistance testing. So I think I wouldn't wait for resistance testing because it's already 18,000 going in the wrong direction - that's a pretty significant DNAemia. So going in the wrong direction.

I personally would not switch to high dose valganciclovir because it's not going to work and it almost never works. It just - there's usually a resistance mutation that's a high level resistance mutation. And almost undoubtedly things will get worse while you're waiting for resistance testing. So I actually would switch to either maribavir or foscarnet.

[00:57:25]

          Management for Suspected Drug-Resistant CMV Infection  

Okay. So here's the algorithm that we mentioned from the guidelines. I will say every - this is the fourth version of the guidelines. Every time we publish this, this is the most popular figure in the guidelines. So there it is.

So one, you identify that there are risk factors and that the patient likely has refractory/resistant disease. Two, you optimize the immunosuppression. You review the drug dosing. You order the resistance testing. If it's a high viral load, then you may wish to use foscarnet or maribavir. And I actually think 18,000 is a pretty reasonable - getting higher viral load. So I probably would go down the foscarnet or maribavir arm.

If it's not high, then you could do intravenous ganciclovir, valganciclovir at higher dose or maribavir.

And then important to realize that you don't want to use maribavir if there's CNS disease or retinitis. So you always want to screen for that. Those are pretty rare, but nonetheless they – maribavir does not penetrate into those spaces.

And then foscarnet in the guidelines. Foscarnet is suggested for high viral loads, usually greater than 50,000. Maribavir tends to work better and have lower - we believe, probably lower rates of resistance developing if there's a lower viral load to start.

And then once you have the genotypic testing, you sort of go through the algorithm and depending on the results you go through, and you pick the best therapeutic options. And depending on how the information you get looks, sometimes I just get the resistance mutation. So I have to actually find in the document - in the guidelines document, I actually find the mutation and look at how resistant it is to various antivirals etc. So you just kind of walk through - walk through the algorithm.

[00:59:06]

          Patient Case #2 (cont’d)

Okay. So there she is 18,000. And this is clearly breakthrough undoubtedly pretty resistant to valganciclovir. So I actually gave her - we couldn't get maribavir quickly for her. So we actually admitted her to hospital, put her on foscarnet induction. She was found to have the UL97 mutation, the M460V, which is one of the top common canonical mutations.

We also switched the belatacept to ciclosporin. And as you can see, she's had - she has a good response to the foscarnet induction. And in the guidelines meeting, we actually talked a lot about maybe induction with foscarnet followed by consolidation with maribavir, not prophylaxis, but sort of starting, just really getting that DNAemia down and then consolidating with maribavir. And because there can be delays in access due to insurance, although the company has a very good program, but still sometimes there can be delays, sometimes foscarnet can give you the initial treatment option.

I personally always keep people in hospital for foscarnet, and I never send anyone home on foscarnet. And I actually have very good outcomes when it's very carefully used.

I then switched the foscarnet to maribavir and famciclovir remembering that maribavir just covers CMV. It doesn't cover HSV, VZV. And so I always think of using it as a combination pill. If somebody has resistant/refractory can be they could be at risk for disseminated zoster.

And she went home and did very well. You can see she had a very low DNAemia. And eventually after a full course of treatment, we switched her to letermovir for a full six months of, at this point, secondary prophylaxis.

And after we stopped the letermovir, she had a little blip of CMV at like 816 IU per ml. And we were really worried. That's very low. But we were worried given the overall context. And this is a very complicated patient who had not tolerated her immunosuppression and had a lot of things go on. So the team was quite worried.

I didn't think we needed to restart maribavir, but we did give a one-time dose of CMV immunoglobulin. And then she subsequently resolved her CMV DNAemia and sailed off into the sunset and has done quite well.

So overall, you know, a case where we've used multiple different agents. We used the resistance testing. And the strongest risk factor for her, I think, was the belatacept treatment. And so really - I - I can almost like smell the belatacept up in the epic chart or the EMR when I - when I get this complex case, I'm like this patient's on belatacept. So, you know, always look for it. Sometimes it's not so obvious or not highlighted.

So I think, where possible, switch to another immunosuppressive agent while they're on the CMV treatment.

[01:01:50]

          Gene Mutations in CMV: UL97 M460V/I      

Here's an example of the guidelines. This is probably hard for you to see from the back, but I just wanted to show you. So I got the information that it was the M460V mutation. And I found it in the chart. So that's a very high level ganciclovir resistance mutation. It results in an EC50 of five to 15-fold higher. So I'm never going to do that - I'm never going to hit that with valganciclovir/intravenous ganciclovir. So I really do need a different agent.

And then one of the cool things that I found out during the guidelines meeting is that this M460V or I mutation actually makes people exquisitely sensitive to maribavir. And overall, in the SOLSTICE trial, they had a statistically better response rate to maribavir compared to other ganciclovir resistance mutations. So that's kind of cool. One little good thing, right, out of all of this.

[01:02:44]

          Patient Case #3

Okay. And now I'll let Atul present his case.

Dr. Humar: Okay. So this is a lung transplant patient D+/R- 10 months post lung transplant. So same situation. He's on valganciclovir prophylaxis at the time this happens, but he's frequently an on and off valganciclovir because of leukopenia. Has a two-week history of fever, fatigue, malaise.

And those are - that's his blood work. Creatinine is mildly elevated at 164 or 1.85, and white count is 2.9. His CMV viral load is 35,500 IU per ml.

[01:03:22]

          Poll 6

So what treatment would you switch to at this point? So:

1. IV ganciclovir;
2. Higher dose oral valganciclovir;
3. Foscarnet;
4. Maribavir; or
5. Other.

Let's see the answer.

[01:03:46]

          Poll 6: Results  

Okay. So IV ganciclovir. So the majority here suggested the foscarnet and the second was IV ganciclovir.

[01:03:56]

          Patient Case #3: After 2 Wk of Full Dose IV Ganciclovir  

So we actually switched this patient initially to IV ganciclovir. And as you can see, what happened is there was no clinical improvement. And that's kind of the - the question in the first case I presented as well. So if a patient - and the case Camille presented. If a patient's on valganciclovir and taking it at a prophylactic dose and they break through with a high viral load, a lot of those patients have true ganciclovir resistance. So, you know, if they present unwell with a high viral load, you have to be careful about using IV ganciclovir in that setting and you should consider an alternative.

But in this patient we did use IV ganciclovir and you can see the viral load went up to 62,000. And the patient did indeed have a very common CMV ganciclovir resistance mutation L595S, which also confers high level ganciclovir resistance.

[01:04:53]

          Poll 7

So at this point, what would you switch the patient to? Would you:

1. Increase the dose of ganciclovir, so double dose;
2. Give foscarnet;
3. Give maribavir; or
4. Do other.

Okay. Let's see the answer.

[01:05:17]

          Poll 7: Results  

Yeah. So the majority suggested foscarnet, and we would typically use foscarnet in that setting as well for that high of a viral load and the patient is clinically unwell.

[01:05:30]

          Patient Case #3 (cont’d)

Although, you know, the renal function is abnormal. So you do need to be quite cautious. This patient indeed was started on foscarnet and the viral load did decrease to undetectable. But what happened is the renal function worsened.

And so the foscarnet had to be prematurely stopped. And then shortly after that, the viral load rebounded, but this time to approximately 10,000 IU per ml.

[01:05:57]

          Poll 8

So what do you do now?

1. Restart foscarnet;
2. High dose ganciclovir;
3. Maribavir;
4. Letermovir; or
5. Other.

Okay, let's see the answer.

[01:06:19]

          Poll 8: Results  

Yeah. So the majority here chose maribavir. And I think this is a really good setting to use maribavir. So the - you know, there's a ganciclovir resistance mutation. The viral load is not terribly high. And the patient also has renal dysfunction there. So all kind of compelling reasons to use maribavir in this setting. And that's what we did.

We also decided to give the patients CMV immune globulin for three doses as well. And the patient had a nice viral load response. And then for secondary prophylaxis, this patient was placed on letermovir for three months and did well.

[01:06:55]

          Summary  

So, Camille, why don't you join me up here and I'll leave the question and answer. So in summary, we hope you enjoyed this. I think it's a pretty exciting time to be in the CMV field. We're entering a new era, as you can see, where multiple diagnostic therapeutics and preventive strategies are being deployed. And this is the troll of transplantation. This is a troll that's hiding out under a bridge, and that CMV is traditionally called the troll of transplantation. And I think we're making good progress.

This is a picture of the guidelines group that met in Montreal last June. So thank you very much. And we'll do some questions.

[01:07:34]

Q&A 

Dr. Kotton: Great. So one of the first questions I think is a pretty straightforward one, but is if CMV viremia worsens after starting treatment, from what time point should you count two weeks to determine refractory CMV? Is it the baseline or is it the peak value?

And I usually say it's from the time that we initiated treatment. Okay. So it's two weeks from the initiation of treatment. The peak is a migratory thing. So you don't know when the peak is are going to happen. So it's sort of two weeks from the onset of treatment.

Dr. Humar: Do you want us to do the post-test questions first?

Dr. Kotton: Oh okay. Sorry.

Dr. Humar: Yeah. Why don't you do that?

[01:08:10]

          Posttest 2

Dr. Kotton: Sorry, sorry. So a heart transplant - heart transplant patient has breakthrough CMV on appropriately renally adjusted valganciclovir prophylaxis. She's compliant. The viral load is 110,000 on plasma. So what is your next therapeutic choice? So this will be interesting to see if you've changed your answers. Would you:

1. Double the dose of valganciclovir;
2. Start intravenous ganciclovir;
3. Foscarnet;
4. Letermovir; or
5. Maribavir.

Go ahead and vote. Go ahead and show us the answers.

[01:08:53]

          Posttest 2: Results  

Okay, so it looks like a lot more people are starting foscarnet. So guidelines, we said, you know, above 50,000 IU per ml probably start foscarnet. Probably, you know, less maribavir in that setting. I'm glad nobody's using letermovir for treatment. So that is - that is great.  

[01:09:17]

          Posttest 2: Rationale  

And doubling the dose of valganciclovir is probably not going to be effective. And it is a high viral load. So we're worried this patient could be getting sicker. So great. Excellent. Lots of learning there.

Okay, so now the Q&A.

[01:09:32]

Q&A 

Dr. Humar: Okay, so the next question. Yeah. So when you're treating patients with CMV, I think we both said you could treat either to negative or you could aim for a center specific threshold. So what - what does your center, Camille, consider as that threshold to aim for if it's not zero?

Dr. Kotton: Yeah. So you know, I often think - so we test on plasma. One of the big issues is if you're using a whole blood assay. And it can actually be hard to tell. Like you have to look pretty hard sometimes in the computer.

Whole blood tends to give a higher overall result. So with whole blood, you may not get to negative. So you may treat for - you could treat for months, but you may not achieve negative. It is a latent virus. It's still in the body. You may still detect it. So that's an important branch point for me, is if it's whole blood, I’ll look at the higher number than if it's plasma. But usually when it's below 200, I'm a lot less worried. I'm a lot less worried about CMV.

So I will often take that as - if it's - if it's double digits or below 200, I'm often like, yeah, we've treated - we've treated well enough. The body will, you know, mop up - mop up the rest. I think that many people keep treating for weeks trying to get the 152 down to, you know, 78, like that's not really necessary. In the guidelines, we talk a lot about what is a clinically significant change. And we recommend thinking about it in log.

And then that it should be a 0.7 log base 10 change when it's especially when the it's below 1,000. So a lot of those numbers are sort of like the same number actually using real-time PCR. And so I think don't over treat. I think we do end up over treating. And then the patients it's expensive and then they can get the cytokines especially leukopenia from the valganciclovir.

What do you think? I'd love talking to you about this question.

Dr. Humar: Yeah, I think - I think this is - this is one of the most common traps that people fall into, is trying to get the viral load down to zero. And it's a - it's just not possible in many patients. And so at our own institution, we use a threshold of 200 IU per ml in plasma. And anything below that, we just call negative actually. And - and we ask the lab - we actually ask the lab to report those as, as less than 200 and not quantify those.

And I think if you do something like that, if you can set a center specific threshold, it will help you immensely in interpretation of these ultralow viral loads. You know, people are trying to treat 50 IU per ml, 35 IU per ml, and they're wondering if they should start maribavir at 75 IU per ml and things like that.

So - and what happens if with these grumbling little low level viremias is many patients will then develop immunity. They'll develop a cellular immune response over time, and they'll actually be able to eliminate that low level of viral load. Although not all patients, you know, some will obviously recur, but - but many patients will.

Dr. Kotton: Often when I have those low level results, I may stop therapy, but I might do some surveillance after treatment. So then I start doing - you know, especially if it's somebody that I think is high risk for a variety of factors. I'll just start doing weekly monitoring and make sure I don't miss the opportunity to treat them at a low level, but I tend to be shorter. I actually think I tend to be shorter on treatment, and I love what he said about his laboratory and how he asked them to report less than 200 as negative.

I asked my laboratory if they'd do that and they said no. Life is better in Canada, I guess.

Dr. Humar: This is a common - common question that gets asked is checking CMV and BAL fluid in the ICU patients?

Dr. Kotton: Yeah. So we covered this in the definitions - of the CMV definitions. And actually, it turns out - I was the one in that definitions group that surveyed the - all these lung transplant programs, including his program in Toronto and my program at Mass General and Duke and multiple other big lung transplant programs.

And it turns out that CMV PCR on BAL is generally really not useful. The higher the number, the more likely they have pneumonitis. But honestly, it depends. BAL is by definition lavage, right? So it depends on how much fluid is put in. We get a lot of numbers, you know, 10 to the six, 10 to the third, all kinds of things. But if it's really high, you can diagnose pneumonitis that way. But otherwise it's really not useful.

And what I found out in my survey is that most of these big transplant programs don't test. Many - so that is actually really helpful. So we largely have stopped doing - I've stopped recommending doing BAL CMV PCRs. That's really - it's a clinical diagnosis. You know it when you see it. You know, the patient has pneumonitis. They often have a significant CMV DNAemia, you know, but also people will shed CMV. And so you don't want to treat all these people that are just shedding because they are in the intensive care unit. So in general we're sort of refraining from sending that.

Dr. Humar: Yeah. Yeah, we had to - we were doing it and eventually we had to ask the lab to stop doing it, because we just didn't know how to interpret all these positive results that we were getting. So I think it's better to just rely on the peripheral viral load and the clinical picture. In the vast majority of settings, there might be some extenuating clinical circumstances where you may specifically want that test.

Dr. Kotton: Okay. And I think that's - I think we're at time. Great. And now there are just a couple - a couple of slides from CCO. And I think the two of us can stay in the front of the room if anybody has any pressing questions or we're available by email. But it was really nice to have you with us today, and we hope you learned a lot from this.

Dr. Humar: Yeah. Thank you. Good job.

Dr. Kotton: Good job.

[END OF TRANSCRIPT]