Is the HIF-PHI class of next-generation kidney drugs doomed in the U.S.?

The FDA’s current full response letter (CRL) for vadadustat — an oral remedy evaluated for the therapy of anemia in sufferers with persistent kidney illness (CKD) — was a giant shock and disappointment for our group. The trials had fairly convincingly demonstrated efficacy as measured by elevating hemoglobin ranges and security as measured by main antagonistic cardiovascular occasions (MACE) for the dialysis-dependent inhabitants—findings that ought to have sealed the approval, however didn’t.

It was perplexing that the FDA determined towards in search of perception from the Cardiovascular and Renal Medication Advisory Committee (CRDAC) for vadadustat, which is an orally administered hypoxia-inducible issue prolyl hydroxylase inhibitor (HIF-PHI). Did the FDA’s expertise with the roxadustat advisory committee assembly, wherein they overwhelmingly voted towards approving the drug for the therapy of anemia related to CKD within the dialysis-dependent and non-dialysis-dependent affected person populations, sound the dying knell for vadadustat and all the HIF-PHI class of medication?

Roxadustat has already been permitted in Japan, South Korea, Chile, and the EU. Vadadustat is permitted in Japan and is presently pending approval within the EU. The FDA appears to be an outlier as a regulatory company by failing to see the optimistic profit/danger evaluation of this drug class. Any potential security considerations with HIF-PHIs that the FDA could have can simply be resolved with a long-term pharmacovigilance plan.

The FDA was primarily involved with venous thromboembolism and vascular entry thrombosis occasions with roxadustat; but there was no indication that vadadustat had that security concern. Information offered on the American Society of Nephrology’s annual assembly in 2021 particularly addressed thromboembolic issues and vascular entry thrombosis in dialysis and non-dialysis sufferers and clearly confirmed that vadadustat was non-inferior to the research comparator, darbepoetin. This could have allayed the considerations that the CRDAC had with roxadustat, whereas distinguishing that vadadustat had a greater security document each when it comes to MACE and of venous thromboembolism and vascular entry thrombosis.

The truth that the FDA didn’t even request a CRDAC for vadadustat means that the regulators could have already made up their minds about this whole class of medication. That is disappointing and unlucky for America’s weak kidney sufferers.

One of many best unmet wants in treating anemia is within the non-dialysis affected person inhabitants, which lacks handy therapy choices. Erythropoietin stimulating brokers (ESAs) are tough to manage. These parenteral medication could require sufferers to go to a healthcare facility for administration, which will be burdensome for sufferers and their caregivers, particularly contemplating the frequency of administration. In distinction, HIF-PHIs are oral brokers that enhance each iron absorption and mobilization, thereby decreasing the necessity for iron administration in anemic CKD sufferers. Contemplating all these components, HIF-PHIs could possibly be efficient and extra handy for non-dialysis CKD sufferers who’re receiving insufficient therapy at this time.

Medicare knowledge point out disconcerting findings: these 65 and older usually tend to have obtained a transfusion to deal with their anemia than iron or ESAs in the course of the two years previous to dialysis initiation. Transfusions are undesirable as a result of they result in allosensitization, probably decreasing the affected person’s donor pool for a future transplant. That is counterproductive to the mission of the federal authorities’s Advancing American Kidney Well being (AAKH) initiative, which goals to enhance kidney transplantation charges. Shifting ahead, will probably be important for stakeholders to guage methods to align these incentives and the flexibility to manage an oral agent at dwelling to deal with anemia, keep away from transfusions, and assist fulfill the targets of improved transplantation charges. Nevertheless, if the FDA has already made up its thoughts concerning the security of this class of medication, sadly, we is not going to see any important enhancements within the therapy of anemia for the non-dialysis affected person inhabitants.

Dialysis-dependent sufferers are completely different from the non-dialysis affected person inhabitants: 80% of people within the former group obtain their goal hemoglobin ranges with average doses of ESAs. Nevertheless, the remaining 10-20% are hyporesponders for quite a lot of causes often associated to irritation.  With a novel mechanism of motion, HIF-PHIs would doubtless be more practical in decreasing hepcidin ranges, thereby mobilizing iron, serving to sufferers keep away from transfusions, and bettering high quality of life associated to increased hemoglobin ranges. One other necessary level is that one of many AAKH initiative’s targets is to extend dwelling dialysis charges to 40-50% of sufferers. Contemplating the burden related to administering parenteral ESAs, HIF-PHIs would add worth to the therapy plan of sufferers who don’t require common visits to a dialysis facility.

Impression of the FDA’s determination on the HIF-PHI drug class

Reflecting on how the FDA’s determination would impression different brokers within the class which might be presently below growth, one has to marvel about daprodustat, one other HIF-PHI presently below evaluate by the FDA. Outcomes revealed within the New England Journal of Medication (NEJM), which have been offered in November 2021 on the American Society of Nephrology annual assembly, confirmed non-inferiority for MACE in each dialysis and non-dialysis populations based mostly on an intention to deal with evaluation—the gold customary for analyzing drug security. MACE non-inferiority of daprodustat was demonstrated among the many dialysis inhabitants in each intention-to-treat and the on-treatment evaluation.

With the CRL for vadadustat, the FDA has made the puzzling determination to extrapolate the security findings of vadadustat within the non-dialysis inhabitants to the dialysis-dependent inhabitants, regardless of non-inferiority knowledge for the latter. In keeping with Akebia, the developer of vadadustat, the FDA has cited hepatocellular damage and thromboembolic occasions, particularly vascular entry thrombosis, as the idea for its rejection. Nevertheless, the outcomes revealed in NEJM clearly present these antagonistic occasions have been no completely different than the lively comparator—hepatocellular damage wasn’t a difficulty in both inhabitants. Desk S7 of the supplemental info, which lists the emergent antagonistic occasions within the security inhabitants, does present a rise in transaminases within the ESA-untreated non-dialysis sufferers handled with vadadustat (1.8% of sufferers) in comparison with darbepoetin (1.0% of sufferers). The distinction, nonetheless, is negligible within the ESA-treated non-dialysis subgroups who obtained both vadadustat (1.2%) or darbepoetin (1.3%).

In my view, this isn’t a sound cause for rejecting the drug within the non-dialysis inhabitants that was studied, and most definitely not within the dialysis inhabitants.

The non-dialysis inhabitants handled with daprodustat demonstrated an elevated incidence of esophageal and gastric erosions, in addition to elevated most cancers danger in comparison with these handled with darbepoetin. Whereas this was not noticed within the dialysis sufferers handled with daprodustat, if the FDA takes an identical stand to vadadustat and extrapolates the security outcomes to each teams, it might jeopardize the approval of daprodustat in each populations.

I strongly urge the FDA to conduct a CRDAC for daprodustat in order that we don’t see a repeat of the non-transparent determination on vadadustat, the place it seems to many who the FDA had unilaterally selected the HIF-PHI class of medication based mostly on the findings with roxadustat. The FDA has apparently conflated considerations with one drug to considerations about all the class. We wish to hear straight from consultants on a CRDAC as they question the sponsor a couple of particular drug previous to an approval determination being made.  The FDA ought to think about every drug by itself advantage as a substitute of these medication as a whole class—each from an efficacy and security perspective.

One other probably helpful drug within the nephrology house, tenapanor, was rejected final 12 months by the FDA citing lower than strong efficacy, however there have been no security considerations.  Nevertheless, the advantages of this drug nonetheless exist on condition that it might cut back the variety of drugs a affected person must take to lower serum phosphorus ranges. Such therapy choices are necessary within the patient-centered tradition we try to realize.  Nephrology has one of many lowest charges of recent drug functions, although almost 40 million People live with some type of kidney illness.

It’s ironic that the AAKH and the Kidney Innovation Accelerator (KidneyX) -— each federal packages that have been conceptualized to enhance nephrology care, sluggish the speed of development of CKD, and reduce the prices related to treating end-stage renal illness care — will not be capable of understand their targets attributable to boundaries to innovation in remedies for kidney illness ensuing from the FDA’s monitor document of rejecting new drug functions for less-than-compelling causes.

I’ve little doubt concerning the efficacy of the HIF-PHIs, and neither does the FDA, for my part. Whereas the FDA reviewers are involved with drug security, they’ve left the door open for drug builders to conduct some extra security research, maybe in smaller teams of sufferers who could also be at increased danger for theoretical antagonistic outcomes. I’m hopeful that the businesses creating these medication — typically small startups — will discover the sources or proper companions to conduct these extra research, though the challenges are nice attributable to price and the time concerned in such trials.

Kidney illness sufferers want entry to progressive therapies to develop therapy selections and enhance high quality of life. The FDA ought to carefully look at whether or not it’s making use of the suitable profit/danger evaluation for brand new medication supposed for this inhabitants. The FDA’s non-transparent rejection of vadadustat within the dialysis inhabitants, the place efficacy is nicely established and there’s no clear security sign, represents a failure by the FDA to behave in the most effective pursuits of the sufferers it was created to serve.

Editor’s Observe: The creator is on the advisory board of Akebia, which obtained the FDA rejection of vadadustat — an oral remedy evaluated for the therapy of anemia in sufferers with persistent kidney illness.

Credit score: sarawuth702, Getty Photos

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