El laboratorio en el tratamiento de la hepatitis C

Notas del editor

• #4: So let’s begin with the patterns of virologic response during therapy with peginterferon and ribavirin. On the Y axis in this graph are the log HCV RNA levels. On the X axis is time, and initially it’s prior to initiating therapy, and then therapy with peginterferon and ribavirin is initiated. So in the blue bar, we have the optimal response, and this is what we want to see in all patients, and it’s now apparent that when you add direct-acting antiviral agents, we see a much greater pattern here where patients undergo a rapid virologic response. That is, after the fourth week of introduction of the therapy you clear virus and you go on to an early virologic response by Week 12, end-of-treatment response, and sustained response. And with genotype 1 hepatitis C peginterferon and ribavirin, you have an opportunity for SVR of about 40%. There are also those that are later responders. You can see here those that fail to undergo a rapid virologic response but do clear virus by Week 12. And these individuals can go on to sustained response but, as you can see here in the yellow bar, the pattern of relapse may occur also, and relapsers in general clear virus a little bit later than those that go on to sustained response. Partial responders, that is, with partial peginterferon and ribavirin responsiveness are those who have greater than a 2-log reduction by Week 12 but fail to clear virus. And null responders, the most problematic individuals with hepatitis C in our practice, are those who have no response; that is, by Week 12 there’s no 2-log reduction, and this is shown here in the orange bar.
• #5: The addition of telaprevir (shown here as TVR) or boceprevir (which is BOC) to peginterferon and ribavirin improves sustained response in genotype 1 patients. Now, both of these new compounds which were approved in May are NS34A protease inhibitors, and they are approved when combined with peginterferon and ribavirin for the treatment of genotype 1–infected individuals. These are those individuals who were previously untreated as well as those who have failed therapy.   This slide just summarizes the phase III trials, showing that in boceprevir- or telaprevir-treated individuals, sustained response rates in genotype 1–naive patients improved from a peg/ribavirin control of 38% to 44% and increased up to 63% to 75%. Substantial improvements were also seen in relapsers, and these individuals are already peg/ribavirin responsive with SVR rates going from 24% to 29%, and when you add boceprevir and telaprevir it goes from up to 69% to over 80%. Partial responders also derive substantial benefit. When we treated with peg/ribavirin, as you can see here in blue, 7% to 15% sustained response; when you add boceprevir or telaprevir to peginterferon and ribavirin, what you see here are improvement in SVR rates from 40% to 59%. You still see an improvement with null responders, but as you can see here, this is the group which is going to be most problematic.
• #6: As we enter the era of direct-acting antiviral agents, proper use of HCV assays are going to be essential for the successful management of hepatitis C treatment with these protease inhibitors. HCV RNA level is important throughout the treatment as it determines whether one is eligible for shortened duration therapy, and you’ll remember that response-guided therapy (or RGT) has become the standard of care as we approach our naive genotype-1 individuals. Also, these assays allow us to adhere and apply futility rules on when to discontinue therapy. The tradeoff for higher sustained response rates with protease inhibitors is a higher risk of resistance, and if you adhere to the futility rules, this minimizes the risk of resistance and also will allow you to avoid some unnecessary adverse events. The assays are also used to assess end of treatment and, of course, sustained response. Additionally, there is now a genetic test available that may help predict response to treatment, and as we move forward we’re going to show you how this genetic test may be used in your practice.
• #7: Some of the key challenges regarding the use of HCV RNA assays includes that the paradigms, that is, the boceprevir and telaprevir labels, use different time points for monitoring HCV RNA. And as we move forward you’re going to have to learn how to use both drugs, and therefore you’re going to need to be familiar with both of the treatment pathways for telaprevir- and boceprevir-based therapies.   There are a variety of available HCV RNA assays that are available, and they do have different quantifiable ranges. There are also different HCV RNA thresholds used for response-guided therapy versus sustained response, and we’re going to discuss this briefly. And finally, there are different HCV RNA thresholds used for defining treatment futility with boceprevir versus telaprevir; that is, different quantitative levels, and we’ll point out these differences to you.
• #8: So let’s talk about the HCV RNA assays. And again as we just mentioned, the lower limit of detection is distinct from the lower limit of quantification. So the definition of lower limit of quantification (or LLOQ) is the lowest HCV RNA concentration within the linear range of the assay. That is, the smallest amount of HCV RNA that can not only be detected but can also be accurately quantified.   The lower limit of detection is the lowest amount of HCV RNA concentration that can be detected with 95% probability to determine the presence or absence of the virus.
• #9: So let’s look graphically at how HCV RNA levels relate to the lower limit of detection and the lower limit of quantification. So this graphic here shows on the Y axis the viral titer, and on the X axis is time, and these would be typical levels we’d see in a successful course of therapy for hepatitis C.   So what you can see here in green as the viral load declines is the HCV RNA assay where it is detectable and quantifiable. And this, as you can see, is over a broad range from log 8 down to somewhere between log 1 and 2.   Beneath log 2 you reach the lower limit of quantification and you can get on your assay a result that says the virus can be detected (as shown here in blue), but it’s not quantifiable.   Finally, there is beneath that a value (here shown in orange) where the viral level is undetectable. And again you’re driving the virus with your therapy down to this level which then, after a period of time with successful therapy, will allow you to achieve sustained response.
• #10: So in the next slide let’s look at the FDA-approved qualitative assays that are available here. And, as you can see, there are a variety of manufacturers here; there are a variety of methods shown in this table, but look at the lower limit of detections for these HCV RNA assays. So, for instance, they range from less than 50 down to 10 IU and, as you can see here, you can use these assays for both diagnosis and monitoring.   The important take-home message from these qualitative assays is that the result you will receive is detected/not detected. So when you are treating patients with these new agents—peginterferon and ribavirin, boceprevir and telaprevir—you have to be very familiar with the report and the assay that you are going to get back. And qualitative assays may be appropriate for some time points but, in general, to make on treatment decisions you’re going to need to use quantitative assays. So let’s now move to the quantitative HCV RNA assays that are shown in the following table.
• #11: So again, similarly to the previous table we have the assay and manufacturer, the method, and again the dynamic range that we previously showed in a graph here. Now let’s look at the lower limit of detections, and what you can see here is that they are highly variable. With these assays, of course, you should use the same assay when you are treating a patient to make sure that the results can be applied consistently during your course of therapy.
• #12: So I would like to show why this is such an important distinction, that is, a detectable vs an undetectable assay result when you treat with boceprevir and telaprevir. As it turns out, sustained response rates are lower when HCV RNA is detectable at key time points during therapy. And this was presented at the International Workshop on Clinical Pharmacology of Hepatitis Therapy and what you see here are boceprevir response-guided therapy and 12-week telaprevir with peg/ribavirin treatment results. On the Y axis again is sustained response. On the X axis here what you see are the clearance rates and SVR rates over time. So you have treatment Weeks 4 through treatment Week 20 for both telaprevir and boceprevir. Light blue is undetectable HCV RNA. Orange is detectable but below the limit of quantification. And then finally, the green bar here is quantifiable and greater than 25 IU.   And just look, for instance, at treatment Week 4 for both boceprevir and telaprevir. As you can see here, at treatment Week 4 with boceprevir you have high SVR rates if you’re undetectable or detectable, but as you move to the right, as you will see here, that undetectable clearly leads to higher sustained response rates. And even by, say, treatment Week 6 or 8 if you’re detectable but below the limit of quantification, your sustained response rate will be lower and that’s important.   For telaprevir you can see a similar pattern. If you are undetectable throughout therapy as opposed to being detectable but below the limit of quantification, your opportunity for sustained response rate is clearly higher.   So it’s important to be able to use these 2 types of assays and be able to interpret them and help guide your response-guided therapy treatment points.
• #13: Let’s talk about the predictive value of baseline HCV RNA for achieving sustained response. This data comes from the ADVANCE study and the SPRINT 2 study with telaprevir and boceprevir, respectively, and what you can see is that higher viral levels in general are associated with slightly lower sustained response rates. So in the ADVANCE study, those with less than 800,000 IU had an overall SVR rate of 78%, those with high viral level (greater than 800,000 IU) had an SVR rate of 74%. In the SPRINT 2 study, in the 48-week peg/ribavirin with 44 weeks of boceprevir arm as well as the response-guided arm, a similar pattern was seen with low viral load individuals having higher SVR rates at 85% and 76% vs 63% and 61% if you had an HCV RNA level that was greater than 800,000 IU.
• #14: Patients responding early can achieve high sustained response rates with shortened therapy. Response-guided therapy is now becoming the standard of care for treatment-naive, genotype 1 individuals, and patients who achieve optimal virologic response at early time points can receive abbreviated or truncated therapy without reducing their chance for an opportunity to achieve sustained response.   So who are the patients that are eligible for response-guided therapy? With boceprevir it’s noncirrhotic treatment-naive patients, previous relapsers, and previous partial responders. The response-guided therapy criterion to qualify is that the individual must achieve undetectable HCV RNA using the assay performance characteristics we just discussed at Week 8, that is, Week 4 of triple therapy, and they must maintain the undetectable level at Week 24 of therapy.   With telaprevir, noncirrhotic treatment-naive patients and previous relapsers can qualify for response-guided therapy, and the criterion are as follows. They must achieve undetectable HCV RNA at Week 4 of triple therapy and maintain this at Week 12. These are the individuals who are eligible and can achieve high sustained response rates.
• #15: So, moving now to the next slide, we’re going to show graphically the response-guided therapy paradigm with boceprevir plus peginterferon and ribavirin in treatment-naive patients. And again, as we’ve just mentioned, this is indicated for all noncirrhotic treatment-naive patients.   So, in the blue here you have your 4-week peg/ribavirin lead-in and, as we’ll talk about shortly, the viral load decline here can provide important information. Boceprevir is then added, and in the top row you can see here that if you have undetectable HCV RNA at Week 8 of therapy, which is treatment Week 4 of boceprevir, as well as treatment Week 24, these individuals can truncate therapy at Week 28, and your opportunity for a sustained response rate is very high and you can simply follow up.   If, however, you are a slower responder—and this is shown in the lower bar here—you get your 4-week peg/ribavirin lead-in (shown in blue), and then boceprevir is added (here in the orange part of the treatment paradigm). But here HCV RNA is detectable at treatment Week 8 but undetectable by treatment Week 24. These individuals are slower responders, and as you’ll see here, these individuals require a total of 32 weeks of boceprevir, so you treat to treatment Week 36 and then you stop the boceprevir and treat with a 12-week peginterferon and ribavirin tail and truncate therapy at 48 weeks. Then you have your follow-up.
• #16: What about treatment-experienced patients? For boceprevir, this is indicated for noncirrhotic relapsers and partial responders to peginterferon and ribavirin therapy. And similar to the treatment-naive paradigm, there’s a 4-week peg/ribavirin lead-in and again undetectable HCV RNA at treatment Weeks 8 and 24, and you truncate therapy at Week 36, that is, all 3 drugs or triple therapy, and you follow up.   What about those that are slower responders, again that are detectable at treatment Week 8 but clear virus at Week 24 while meeting the futility rules? Well, similar to the treatment-naives, you stop the triple therapy at Week 36 and continue peginterferon and ribavirin for 12 weeks, and you subsequently follow up after that to see if you achieve sustained response.
• #17: So now let’s look at the response-guided therapy paradigm with telaprevir with peginterferon and ribavirin in treatment-naive patients. Again it’s a response-guided therapy paradigm where telaprevir is given for 12 weeks with peginterferon and ribavirin. HCV RNA is measured at Weeks 4 and 12 and if undetectable at both time points or an extended rapid virologic response, one simply truncates therapy at Week 24. So here you see you get 12 weeks of triple therapy followed by 12 weeks of peginterferon and ribavirin.   Let’s go now to those who are slower responders. So this is shown in the second row. Here, HCV RNA turns out to be detectable with less than 1000 IU at treatment Week 4, and you continue therapy to Week 12 where you can be undetectable or detectable but again less than 1000 IU. Here then you continue therapy with just peginterferon and ribavirin for a total of 36 weeks. Of course, there is a Week 24 detectable futility rule here, but if you meet this futility rule then you treat for a total of 48 weeks, so it’s 12 weeks of triple therapy followed by 36 weeks of peginterferon and ribavirin, and still your opportunity for sustained response is substantial.
• #18: Let’s now look at response-guided therapy paradigm with telaprevir and peginterferon in treatment-experienced patients. Now, for response-guided therapy for previous relapsers, this is actually the same paradigm as naives. So it’s undetectable at Weeks 4 and 12 and extended RVR, and then you complete 12 weeks of peginterferon and ribavirin and you truncate therapy.   And again the AASLD guidelines suggest that response-guided therapy could be considered for prior partial responders, but the package insert with telaprevir actually suggests 48 weeks of therapy. And again it is our practice that we follow the package insert here, and partial and null responders get a total of 48 weeks of therapy with, of course, the 12 weeks of triple therapy at the beginning.
• #19: So let’s look at the HCV RNA assay characteristics for response-guided therapy with boceprevir or telaprevir. You need again, as specified in the package insert, a quantitative assay with a lower limit of quantification of less than 25 IU/mL and a lower limit of detection of approximately 10-15 IU. Confirmed detectable but below the limit of quantification HCV RNA result should not be considered equivalent to an undetectable HCV RNA result. I urge all of you who treat hepatitis C to read your assay reports very carefully with this and make sure that indeed it is not detectable.
• #20: We also use the predictive value of response to a 4-week peginterferon/ribavirin lead-in, and again this is with boceprevir. We will talk later about a genetic test which helps predict peg/ribavirin responsiveness. The lead-in is the peginterferon/ribavirin responsiveness and, indeed, if you have a greater than 1 log reduction in HCV RNA following the 4-week peg/ribavirin lead-in, this strongly predicts sustained response when you receive boceprevir. If your HCV RNA decline is less than 1 log, you are less peg/ribavirin responsive and your opportunity for SVR rate is lower. And again, in both treatment-naive and in treatment-experienced patients, as you can see here, the odds ratios were extremely high for both treatment-naive as well as treatment-experienced patients. So again don’t forget when using boceprevir that your 4-week peg/ribavirin lead-in provides valuable data.
• #21: What you can see here is the treatment paradigm, that if you reach Week 12 and your HCV RNA is greater than 100 IU—and this should be done with a quantitative assay—that you need to stop all therapy. And the futility rules now have been modeled, and indeed by this time there is no opportunity for you to achieve sustained response rate.   The same thing is true at Week 24. You should, if your HCV RNA is detected, also truncate therapy; your opportunity for SVR rate is essentially zero.
• #22: Let’s look at the telaprevir futility rules. Here there are the key time points: Weeks 4, 12, and 24. At Week 4 using a quantitative assay and at Week 12 using a quantitative assay, if the HCV RNA is greater than 1000 IU, then you stop therapy here.   What about Week 24 futility rule? Well, this is identical to the boceprevir futility rule. That is, if it is detectable, then you truncate and stop the peginterferon and ribavirin; there is no opportunity here to achieve sustained response.
• #23: So let’s look at the end of end of treatment assays that we use when you’re completing therapy with boceprevir or telaprevir. So, the end of treatment response is defined as an undetectable HCV RNA at the end of treatment. And again in both the package inserts this should be with an assay using a sensitivity of less than or approximately 10-15 IU. If you are detectable but below the limit of quantification at any time on treatment, as we showed previously, this predicts lower sustained response rates.
• #24: So, previously sustained response to peginterferon and ribavirin was defined as the absence of detectable HCV RNA in the serum using an assay with a sensitivity of at least 50 IU/mL 6 months after the end of therapy. This has recently been revised by the FDA in both the boceprevir and telaprevir package inserts and is now HCV RNA less than 25 IU or beneath the lower limit of quantification (or LLOQ) 6 months after the end of treatment. And please note this is a new guideline that was set forth for the era of direct-acting antiviral agents.
• #25: So, in summary, the use of HCV RNA assays in managing patients receiving boceprevir or telaprevir, a quantitative assay with a lower limit of quantification of less than or equal to 25 IU/mL and a lower limit of detection of approximately 10-15 IU/mL should be used.   A very important concept: HCV RNA less than the lower limit of quantification is not identical to an undetectable HCV RNA. An undetectable HCV RNA level on treatment is what qualifies you to proceed with response-guided therapy. And finally, an HCV RNA less than the lower limit of quantification is appropriate for assessing sustained response.   And again graphically you can see here below the qualification or the endpoint for both telaprevir and boceprevir. And again these are nicely summarized for you as you move forward for treating your hepatitis C patients.
• #26: So just by way of review, IL28B, which was discovered only a few years ago, is the strongest baseline predictor of sustained response with peginterferon and ribavirin. So this is a paper from Thompson and colleagues from the IDEAL study showing the odds ratios for pretreatment predictors for sustained response. And you see here the traditional predictors that we’ve always expected, and they include fasting glucose, race, fibrosis level, and viral level. But look at the odds ratios for IL28CC versus non-CC at the bottom here. And as you can see here, IL28CC more strongly predicts SVR than any of the other traditional factors.
• #27: IL28B genotype also predicts likelihood of achieving sustained response with boceprevir or telaprevir.   These are the results from the phase III SPRINT 2 and ADVANCE studies with boceprevir and telaprevir. Recognize that IL28B was not actually discovered when these initial trials were started, so that these turned out to be retrospective analyses, but the results from the retrospective analyses still provide useful data for us. And what they show us is that if you are IL28CC, you’re more likely to achieve sustained response than you are if your IL28 status is less favorable, that is, CT or TT. And that’s true for both telaprevir and boceprevir, as you can see on these slides here where CCs get high sustained response rates, and the addition of boceprevir and telaprevir while improving SVR rates in the more difficult to treat individuals numerically are still lower than the most favorable IL28CC.
• #28: I think as you try to incorporate IL28B into your practice, what you’re going to find is that IL28B CC genotype strongly predicts the likelihood of truncated therapy with boceprevir or telaprevir. And again, based on these retrospective analyses from the SPRINT 2 and ADVANCE studies, what you see here on the Y axis for both of these are those percent who are eligible for response-guided therapy, that is, truncated therapy. And if you’re IL28CC, your opportunity for truncated therapy or response-guided therapy is much higher. And that’s a reason to consider ordering this test, because oftentimes patients are very interested to know if they have an opportunity to be treated for a shorter duration of therapy.
• #29: So, again there are no firm guidelines yet, and we are going to need more prospective data, but IL28 genotyping can be considered prior to therapy if more information about the probability of response or the treatment duration is desired. It’s certainly available, and there are 2 commercial assays that are now available. If patients have the favorable CC genotype, the likelihood of sustained response rate is high with peg/ribavirin, but triple therapy can allow shorter duration therapy and, in one study, albeit based on a retrospective analysis, higher sustained response rates.   It is these unfavorable CT and TT genotypes that really get the most benefit from boceprevir and telaprevir addition.   What about in treatment-experienced individuals? Here, IL28B genotyping is probably less useful. If you have good viral kinetics when you assess your treatment-experienced patients, you don’t need it at all, simply because IL28B predicts viral kinetics. If you have them, you actually have the actual data, and in those circumstances IL28B is not required.
• #30: Let’s quickly talk about the HCV RNA genotype and subtype. Again we’ve known that the hepatitis C virus is classified into 6 major genotypes. Genotype 1A and 1B are most common in the United States; they are approximately 75% of the individuals, and subtype 1A is more common than subtype 1B. Determining the major genotype is recommended for proper clinical management and predicting the likelihood of response. There’s no current recommendation right now regarding HCV subtype testing.
• #31: However, genotype is now becoming more important in the era of direct-acting antiviral agents, and this slide from the telaprevir studies shows that genotype 1A with telaprevir is associated with somewhat numerically lower sustained response rates than genotype 1B, here shown in orange. And these are from the telaprevir-naive as well as the telaprevir nonresponder trials.
• #32: We see a similar pattern in boceprevir, and again this was data from the phase III trials showing that in both treatment-naive and treatment-experienced individuals, again numerically higher SVR rates are seen with genotype 1B than 1A.
• #33: So what are the commercially available HCV RNA genotype assays? Well, they’re listed here. They all rely on a variety of methods and, fortunately, they’re well standardized, and incorrect typing among the major genotypes is extremely uncommon, less than 3%.
• #34: Now, it’s important to know as we enter the era of direct-acting antiviral agents that we’re going to be dealing with resistance with virtually all of these new direct-acting antiviral agents. Resistance-associated variants occur naturally, and they’re present in approximately 5% to 7% of subject samples prior to initiation of therapy. However, they don’t appear to negatively impact your opportunity to achieve sustained response. However, when you have a patient who is failing to respond on protease inhibitor–based therapy—that is, telaprevir or boceprevir now—these resistance-associated variants are selected and they are enriched. So, the important thing is what happens to them, and this preliminary data shows that following treatment failure these resistance-associated variants decline over time after the withdrawal of the protease inhibitor. That is, once you remove the pressure of the protease inhibitor, the resistance-associated variants decline in quantity. They can remain detectable, however, for up to 2.5 years.   Now, why is that we see more of these with 1A than 1B? It’s likely due to a lower genetic barrier to resistance - that is, the number of mutations required to overcome virologic activity of your protease inhibitor regimen - with genotype 1A is lower than it is with 1B.   How can we minimize the risk of resistance? Well, the most important thing to do is adhere rigorously to the futility rules. They were written and the data was used to make sure that, number one, if you adhere to these futility rules you will not be losing the opportunity to achieve sustained response. You also need to ensure patient adherence. You need to be taking your protease inhibitors on time. You need to make sure that doses are not missed. You need to aggressively manage all of the peginterferon, ribavirin, and direct-acting antiviral side effects to maximize your ability to achieve sustained response as well as to minimize the opportunity for the emergence of resistance-associated variants.
• #35: What about resistance testing? Well, it turns out a commercial resistance test is now available, and this provides genetic sequence for the nonstructural proteins NS3 and NS4A of HCV genotypes 1A and 1B.   What’s the role of resistance testing prior to treatment? Well, it’s not clear. There are no current recommendations to perform resistance testing for patients failing therapy at this time, and as we move forward, more data’s going to have to be collected before we really get an opportunity to find out what the correct role of resistance testing is going to be.
• #36: So, in summary, IL28B testing may be considered prior to therapy if more information about probability of response or treatment duration is desired. And remember, IL28CC-genotype individuals have a high opportunity to achieve sustained response rate with 6 months of therapy.   What about HCV subtype testing? There’s no current recommendation to test prior to treatment, but patients with genotype 1B may be counseled that their opportunity for sustained response rate is numerically slightly higher than individuals who are genotype 1A.   What about HCV RNA resistance testing? There’s no current recommendation regarding testing at baseline or upon treatment failure now. We’re going to have to await additional studies before we can provide additional recommendations.