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FDA Sets High Bar for Real-World Evidence in Rare Diseases

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Real-world data (RWD) can be used to create historical control groups for clinical trials in rare diseases where a randomized controlled trial (RCT) is not feasible. But what happens when the US Food and Drug Administration (FDA) doesn’t accept it?

Since passage of the 21st Century Cures Act in 2016, FDA has promoted the use of real-world evidence (RWE) to increase the efficiency of clinical research. However, according to
FDA’s 2018 RWE framework, the use of RWE is primarily restricted to evaluating safety
(eg, monitoring postmarketing safety). It can only be used in limited circumstances to inform decisions about effectiveness.

When it comes to regulatory decisions about product effectiveness, FDA’s framework suggests that RWE can be used to support changes to labeling about product effectiveness, including adding or modifying an indication, such as a change in dose, dose regimen, or route of administration, adding a new population, or adding comparative effectiveness data.

So, where does that leave sponsors who want to compare the results of a single-arm clinical trial to a real-world historical control arm to demonstrate the effectiveness of a new product? Unfortunately, the FDA has set a very high bar.

Regulatory “Fitness” in Rare Disease Clinical Trials

At a joint FDA-National Institutes of Health workshop in May 2022, titled “Regulatory Fitness in Rare Disease Clinical Trials,” Katie Donohue, Director of the Division of Rare Diseases and Medical Genetics in the Center for Drug Evaluation & Research, said that the challenges facing sponsors attempting a single-arm approach to develop a first therapy for a rare disease are so daunting that development programs only “work when you are very lucky.” In particular, she pointed out that single-arm studies are vulnerable to changes in rare disease natural history.

Changes in natural history, response assessment, and standard-of-care therapy can have a dramatic effect on time-to-event endpoints such as overall survival (OS). So, for a single-arm trial, FDA recommends concrete, confirmed endpoints “like an x-ray or blood test.”

These comments highlight the strong preference FDA has for RCTs, in general, and even for rare diseases, where it is often extremely challenging to conduct an RCT with sufficient statistical power to demonstrate effectiveness.

FDA Has Set the Bar Very High

FDA’s draft guidance, titled Considerations for the Use of Real-World Data and Real-World Evidence to Support Regulatory Decision-Making for Drug and Biological Products, acknowledges the potential utility of using RWD in interventional studies, including “to serve as a comparator arm in an external control trial.” However, the guidance focuses heavily on the use of RWD/RWE in non-interventional studies, such as observational cohort studies and case control studies that evaluate the safety and effectiveness of a product in routine medical practice and are not governed by a research protocol.

Although FDA is not opposed to the idea to using RWD to construct historical control groups – also referred to as an external control arm – it is highly critical of that approach as the basis for regulatory approval of a novel drug.

Recently, Y-mAbs Therapeutics found this out the hard way. In collaboration with Memorial Sloan Kettering Cancer Center (MSKCC), Y-mAbs has developed a targeted radiolabeled antibody called 131I-omburtamab for the treatment of neuroblastoma that has metastasized to the central nervous system (CNS). This ultrarare pediatric indication affects only about 20 patients per year in the United States, and there are no approved therapies.

With traditional treatment approaches – surgery, radiotherapy (RT), and chemotherapy – most patients only survive a few months after diagnosis of CNS metastases. For about one third of patients who survive long enough to receive 2 or 3 treatment modalities, median survival is about 15 months. So, the clinical team at MSKCC, led by Dr. Nai-Kong Cheung and Dr. Kim Kramer, developed 131I-omburtamab, an anti-B7-H3 antibody, which they inject directly into the cerebrospinal fluid via an Ommaya catheter, as an adjunct to standard therapy. The goal is to eradicate residual tumor cells and increase the chance of achieving a cure.

The team at MSKCC has been studying the safety and effectiveness of 131I-omburtamab in this poor-prognosis patient population since 2004. In that timeframe, they have treated more than 100 children with CNS neuroblastoma, of whom about 40% have survived more than 8 years. Their treatment protocol demonstrated a median OS of 51 months, a milestone that clinical experts consider quite extraordinary.

Fast Forward to 2015

In 2015, Thomas Gad, whose daughter was successfully treated at MSKCC for CNS neuroblastoma, founded Y-mAbs Therapeutics to further develop 131I-omburtamab and get it approved in the US, so other children could have access to this potentially lifesaving drug.

To demonstrate the effectiveness of 131I-omburtamab, the company conducted its own single-arm multicenter trial in 50 patients, principally to confirm the results from the single-institution MSKCC trial and demonstrate objective responses to the drug. Given the rarity of this indication, an RCT was not feasible.

Y-mAbs then set out to obtain patient-level data from children with CNS neuroblastoma treated outside MSKCC and construct an external control arm for comparison with the MSKCC trial population. They succeeded in identifying only one suitable database, a neuroblastoma registry in Germany, and they were able to extract patient-level data from 120 patients who had a first recurrence of neuroblastoma in the brain. In collaboration with the FDA, Y-mAbs designed the comparative analysis using a propensity score model.

After carefully balancing the intensity of standard treatment with surgery, RT, and chemotherapy (modality group 2), the Y-mAbs biometrics team identified a cohort of 34 patients from the external control arm that they could compare to 89 patients in the MSKCC study. A comprehensive propensity score model that controlled for potential confounding factors demonstrated a 42% improvement in OS (hazard ratio = 0.58) compared with the external control arm. Sensitivity analyses showed a consistent treatment effect (hazard ratios ranged from 0.42 to 0.66) in favor of 131I-omburtamab.

Y-mAbs also went one step further, restricting the analysis to only patients in first recurrence, adjusting the index dates to control for immortal time bias, and removing patients from the external control arm treated prior to 1997. That analysis, which represents the best possible match between the populations, showed a 52% improvement in OS (Figure 1).

Figure 1.   Overall survival in patients in modality group 2 treated at first recurrence comparing index dates A vs D and excluding NB90 from external control arm

These data, along with supportive data from the multicenter trial, were the basis for the Y-mabs Biologics License Agreement filed in March 2022. However, after careful review of the data, FDA’s Oncology Division concluded that the external control arm is “not fit for purpose.” FDA argued that limitations of the data and multiple sources of potential bias resulted in a large degree of uncertainty regarding whether the observed OS difference was due to 131I‑omburtamab or differences between the populations, or a combination of these factors. FDA also had doubts about the objective response data.

FDA Oncologic Drugs Advisory Committee (ODAC) Meeting

At the ODAC meeting on October 28, 2022, the FDA presented its case that the 2 populations were not comparable, primarily because of differences in treatment intensity and era of therapy. They pointed out that none of the patients in the external control arm received craniospinal irradiation, a form of RT perceived to be more effective than the standard focal or whole-brain RT given to the German patients. However, there are no published studies to show that it is more effective in neuroblastoma. The FDA also presented evidence that clinical outcomes for CNS neuroblastoma have improved over time. Consequently, FDA restricted its analysis to only those patients in the external control arm who were treated from 2004 to 2015, the time period corresponding to the MSKCC study.

After adjusting for all these potential confounders, including immortal time bias, the FDA analysis showed a hazard ratio of 1.0, suggesting no OS benefit.

Ultimately, the committee voted unanimously that the Applicant had not provided sufficient evidence to conclude that 131I-omburtamab improves OS in the proposed indication. The committee wanted to see more data. Unfortunately, that may not be feasible.

This case sends a strong message regarding the rigor of data that FDA expects when establishing effectiveness based on a time-to-event endpoint in a single-arm trial with comparison to an external control arm, even in a rare disease where it exercises regulatory flexibility. The consequence of this ODAC decision means that sponsors will face a high bar when attempting to demonstrate that an external control arm is “fit for purpose.”

Jeff Riegel, PhD
SVP, Scientific Communications, ProEd Regulatory
Jeff combines his scientific expertise in molecular biology and immunology with more than 25 years of global healthcare agency experience guiding medical and regulatory communication strategies for biopharma companies. Jeff helps clients prepare for FDA Advisory Committee meetings and other health authority interactions. Connect with Jeff on LinkedIn.

The Saga of PI3K Inhibitors: Part 2 – The shifting role of overall survival

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In Part 1 of our blog series on the saga of PI3K inhibitors, we reviewed the FDA’s recent Oncologic Drugs Advisory Committee (ODAC) meeting on April 21, 2022, to discuss the agency’s concerns about PI3K inhibitors (PI3Kis). The panel voted resoundingly (16 yes votes; 1 abstention) that future approvals of PI3Kis should be supported by randomized data that would allow an assessment of overall survival (OS)—an action that makes accelerated approvals less likely and more difficult to obtain in slow-growing cancers with a long median survival.

At the heart of the FDA’s concerns with the PI3Ki class is an apparent excess of deaths in clinical trials of PI3Kis, indicating a potential detriment to long-term survival in patients who were treated with PI3Kis. However, assessing OS in patients with indolent blood cancers, who have very long lifespans, can be exceedingly difficult—and the results are not always interpretable.

In this second installment of this blog series, we will focus on the OS data for PI3Kis presented by the FDA, the complexities of evaluating OS in blood cancers with long lifespans, and the broader regulatory implications of an increased focus on OS as a safety endpoint in patients with indolent diseases.

Regulatory pressure to withdraw PI3Kis continues…

The Class 1 phosphatidylinositol-3-kinases (PI3Ks) are master regulators of cell proliferation, growth, survival, motility, and immune cell function that are highly dysregulated in blood cancers. Four PI3Kis (idelalisib, duvelisib, copanlisib, and umbralisib) have been approved by the FDA for B-cell malignancies such as chronic lymphocytic leukemia (CLL), and indolent non-Hodgkin’s lymphomas (iNHL), including marginal zone lymphoma (MZL) or follicular lymphoma (FL). Please see Part 1 for additional background on PI3Kis.

As of writing this post, all accelerated approvals for PI3Kis in iNHL have been withdrawn, mostly due to a failure to complete a confirmatory trial. These withdrawals also likely reflect the ODAC decision in favor of a requirement for randomized data to support future approvals for PI3Kis (rather than single-arm trial data, which are often used to support accelerated approvals in oncology).

Currently, there are 2 PI3Kis (idelalisib and duvelisib) with full approval in later-line treatment of CLL that remain on the market.

Since the April ODAC, however, the FDA has increased pressure on sponsors to withdraw even fully approved indications for PI3Kis on the basis of a potential detriment to overall survival. The most recent development came on June 30 with a warning issued by the FDA that Secura Bio’s PI3Ki, duvelisib, may increase the risk of death when used as a third-line treatment for patients with CLL. Duvelisib received full approval for CLL in 2018 on the basis of the phase 3 DUO trial. The FDA warning stated that the agency plans to hold a future public meeting to discuss the updated overall survival data of duvelisib, and whether duvelisib should continue to stay on the market – hinting that another potential ODAC meeting may be on the horizon.

Since the April ODAC, however, the FDA has increased pressure on sponsors to withdraw even fully approved indications for PI3Kis on the basis of a potential detriment to overall survival.

“The ultimate safety endpoint”: Do PI3Kis lead to a detriment in OS?

The FDA views OS as “the ultimate safety endpoint” because it encompasses deaths directly caused by adverse events related to the drug, and deaths that might be related to long-term side effects of the drug, which can be difficult to identify. Importantly, the FDA specifies that OS “does not require [the] same statistical considerations when used as a primary safety endpoint.” The FDA’s viewpoint is straightforward: The ultimate goal with any drug therapy should be to prolong life without inflicting long-term harm. From this viewpoint, OS has a dual purpose of providing information about the effectiveness of a drug, while also informing safety.

The FDA presented data at the April ODAC showing that in six phase 3 randomized trials for the approved PI3Kis, most had OS hazard ratios (HR) >1 (Figure 1) . An HR >1, based on Kaplan-Meier estimates, suggests that more patients died on the experimental arm (in this case the PI3Ki) than on the comparator arm. In 3 trials with idelalisib (the first approved PI3Ki drug), there was a much higher risk of death in the idelalisib arm, with a nearly 5× greater risk of dying in the 313-0124 trial in iNHL, and a more than 3× greater risk of dying in the 312-0123 trial in CLL.

The FDA views OS as “the ultimate safety endpoint” because it encompasses deaths directly caused by adverse events related to the drug, and deaths that might be related to long-term side effects of the drug, which can be difficult to identify.1

The OS results in trials with other PI3Kis across various patient populations and treatment regimens (DUO, CHRONOS-3, and UNITY CLL) did not show a survival imbalance as extreme as that observed in the idelalisib trials. Although most of these trials exhibited OS HRs >1, the 95% confidence interval was very wide and included 1. The CHRONOS-3 trial of copanlisib in iNHL was an exception, with an HR of 0.87 (95% CI: 0.57, 1.35) (Figure 1).

Figure 1: Summary of overall survival data and toxicity risk in FDA-approved PI3Kis. Slide 45 of the FDA presentation at the April 21 ODAC meeting.   

The FDA interprets these data to indicate an overall pattern of potential detriment to survival in patients treated with PI3Ki as a class, possibly linked to an increased risk of infection or immune-mediated adverse events, or unidentified long-term effects of PI3Kis that may negatively impact the efficacy of subsequent therapies.3

Imbalances in OS are not unheard of in blood cancer clinical trials…

The FDA repeatedly describes a pattern of detriment in survival with PI3Kis as “unprecedented” in oncology, but are unfavorable imbalances in OS in blood cancer trials really unprecedented? A quick review of the literature disproves this notion.

The Bruton’s tyrosine kinase inhibitor (BTKi) ibrutinib was approved for previously untreated CLL in January 2019 on the basis of the iLLUMINATE trial. At the final analysis from iLLUMINATE, there was an OS HR of 1.08 in favor of the comparator arm. Similarly, venetoclax, a B-cell lymphoma 2-targeted inhibitor (BCL2i), was approved for first-line CLL treatment in May 2019 on the basis of the CLL14 trial with an initial OS HR of 1.24 at the time of approval, although with 4 years of follow-up the OS HR improved to 0.85, albeit with results that were still not significant. Importantly, both ibrutinib and venetoclax are approved in multiple indications and are considered successful and paradigm-shifting drugs, despite never having shown a significant improvement in OS in blood cancers (nor have they definitively ruled out potential detriment).

These examples cast doubt on a narrative that PI3Kis are somehow uniquely detrimental to survival in indolent blood cancers. Rather, the problem with evaluating OS in blood cancer trials may be a reflection of the disease itself, rather than any particular class of drugs.

These examples cast doubt on a narrative that PI3Kis are somehow uniquely detrimental to survival in indolent blood cancers. Rather, the problem with evaluating OS in blood cancer trials may be a reflection of the disease itself, rather than any particular class of drugs.

The complexities of evaluating OS in blood cancers with long lifespans

There are several considerations that make OS data difficult to interpret in blood cancers with very long life expectancies. Most importantly, because there are few deaths, it is not feasible to appropriately power these trials to assess OS with statistical confidence. As a result, OS analyses tend to have wide confidence intervals that are highly unstable over time. For these reasons, OS is not used as a primary endpoint in indolent blood cancers. Instead, studies are typically powered for the primary endpoint of progression free-survival (PFS), which provides more clearly interpretable results. OS is often included as a secondary or exploratory endpoint, but is not usually considered conclusive.  

The interpretation of OS is further challenged by trial design realities in indolent diseases; for example, patients may go on to receive several different lines of therapy before their death and trials often include a crossover arm (wherein patients on the control arm may choose to receive the experimental treatment after disease progression). Consequently, analyses of OS may be confounded and rendered uninterpretable. Finally, identifying the cause of death is fraught with difficulty when a large number of deaths may occur years after patients have discontinued study drug.

It is also worth mentioning that COVID-19 deaths present a unique challenge to interpreting OS in indolent blood cancers (and, to some extent, all clinical trials affected by the pandemic) not only because of the timing of COVID-19 infection waves and deaths, but also because of shifts in standard of care that can no longer be controlled for by randomization. Given these circumstances, it is possible, or even likely, that a pattern of OS detriment seen with the newer PI3Kis in recent clinical trials is a chance finding, rather than a real reflection of risk.

How should sponsors use OS to support benefit-risk assessments?

If it is not possible to adequately power a trial for OS or to interpret the results, how exactly should an “assessment” of OS be performed to support benefit-risk evaluation of PI3Kis? When asked this question directly by a panelist, the FDA fell back on its stance that the burden is on sponsors to prove that PI3Kis are not producing a detriment to survival – a difficult situation for drug developers. However, the FDA provided few clues as to what it is looking for (see slide 75 of the FDA presentation).  

Sponsors developing new PI3Kis should be prepared to incorporate detailed analyses of the causes of death on each arm into study protocols, with the goal of providing assurance that the experimental arm is not causing excess deaths related to immune-mediated toxicity or an increased risk of infection due to PI3K inhibition. This type of analysis would require a much more in-depth investigation than is typically done, given the problems discussed above with tracking deaths that occur long after a patient has left the study. Sponsors should also attempt to design future studies so that the OS data are better able to withstand an increased level of scrutiny. For example, trial designs that include an option to cross over to the experimental arm after progression may not be advisable.

Ultimately, even following the FDA’s suggested changes to clinical trial design, there is no guarantee that OS can be evaluated with sufficient statistical clarity to definitively show that PI3Kis are not causing a detriment to survival.

What do the experts think?

Notably, not all physicians agreed with the FDA’s conclusion of a pattern of detriment to OS with PI3Kis. In a public docket comment in response to the April ODAC meeting, Jennifer Brown, MD, PhD, “urge[d] caution in the interpretation of trials in different clinical settings,” “as well as the interpretation of long term follow-up data which may be confounded by subsequent therapy choice and crossover study design.” Dr. Brown went on to note that PI3Kis have provided “transformative and life-saving” benefits, and “in patients who are heavily pretreated, as is the case with all the existing approvals and the drugs in development, the toxicity is readily managed.”  

In the context of excellent benefits in progression-free survival with PI3Kis and high unmet need for alternative therapies in heavily pre-treated patients, many physicians still view the benefit-risk profile for PI3Kis as favorable. On July 1, the CLL Society sent a letter to the FDA that received signatures of support from 40 of the top CLL/SLL physicians in the country, which urged the FDA to maintain approved PI3Kis as an option for patients with CLL:

“Going forward and looking more widely at the CLL therapeutic landscape, safety must never be compromised. But drug innovation should continue to be encouraged. We believe the FDA can leverage the power of electronic medical records and real-world data to further assess the safety of PI3K inhibitors. Delays associated with the wait for overall survival data have already started to dampen research efforts in CLL and have slowed patient access to potentially life-saving therapies. CLL is a chronic cancer, and patients are often exposed to multiple therapies over the span of their disease. Survival data will come too slowly for many patients and will never be ‘statistically pure.’ CLL Society and many others have pushed for crossover in clinical trials to ensure equipoise, which while further confounding the survival data, saves lives. In the opinion of CLL Society, clinical trial design focused on overall survival endpoints will ultimately delay or deny the best possible care to patients with CLL.”

Coming Next: Part 3 – How should dose optimization be conducted in drug classes with known immune-mediated toxicity risks?

The FDA has raised concerns that for the approved PI3Kis, dose modifications or treatment interruptions due to AEs are too common in clinical trials, indicating that the dose may be too high. The dosing regimen for all approved PI3Ki was selected based on standard, phase 1, single-arm dose escalation studies in small cohorts of patients. However, in the FDA’s view, this standard approach may lead sponsors to default to selecting the maximum tolerated dose, rather than the optimal (likely lower) dose that might achieve similar efficacy with less toxicity.

InIn Part 3 of this series, ProEd will review the panel discussion of how best to optimize drug dosing for PI3Kis, the broader FDA regulatory initiatives (ie, “Project Optimus”) surrounding dose optimization, and how these considerations may impact clinical trial design and dose-finding studies for targeted oncology drugs that modulate the immune system.

Angela W. Corona, PhD
Scientific Director, ProEd RegulatoryAngela is a Scientific Director for ProEd Regulatory. She is responsible for helping sponsors navigate complex regulatory communications such as FDA advisory committee meetings. She develops clinical and regulatory strategy along with high-quality scientific and medical content across a wide range of therapeutic and drug development areas. Angela received her PhD in Neuroscience from The Ohio State University and completed her postdoctoral training at Case Western Reserve University in Cleveland, Ohio.

References

  1. Pazdur R. The saga of PI3K inhibitors in haematological malignancies: survival is the ultimate safety endpoint. Lancet. 2022 April 14 [Online ahead of print]. https://doi.org/10.1016/S1470-2045(22)00200-5
  2. FDA Presentation, Introductory Comments; Presented by Nicole Gormley. Oncologic Drugs Advisory Committee Meeting. Phosphatidylinositol 3-Kinase (PI3K) Inhibitors in Hematologic Malignancies. April 21, 2022. https://www.fda.gov/media/157837/download
  3. FDA Briefing Document. Oncologic Drugs Advisory Committee Meeting. Phosphatidylinositol 3-Kinase (PI3K) Inhibitors in Hematologic Malignancies. April 21, 2022. https://www.fda.gov/media/157762/download
  4. Moreno C, et al. First-line treatment of chronic lymphocytic leukemia with ibrutinib plus obinutuzumab versus chlorambucil plus obinutuzumab: final analysis of the randomized, phase 3 iLLUMINATE trial. Haematologica. 2022 Jan 13 [Online ahead of print]. https://doi.org/10.3324/haematol.2021.279012.
  5. Fischer K, et al. Venetoclax and obinutuzumab in patients with CLL and coexisting conditions. N Engl J Med. 2019;380(23):2225-2236. https://pubmed.ncbi.nlm.nih.gov/31166681/
  6. Al-Sawaf O, et al. Minimal residual disease dynamics after venetoclax-obinutuzumab treatment: extended off-treatment follow-up from the randomized CLL14 study. J Clin Oncol. 2021;39(26):4049-4060. https://pubmed.ncbi.nlm.nih.gov/34709929/

The Saga of PI3K Inhibitors: Part 1 — The ODAC Decision

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The FDA’s Oncology Division has recently taken a hard stance on PI3K inhibitors, a novel class of drugs that inhibit various isoforms of phosphatidylinositol 3-kinase (PI3K) and are approved for treating blood cancers. Recent actions by the FDA, including withdrawing some approved indications, indicate that they will likely be seeking a higher bar for new approvals of PI3K inhibitors for certain blood cancers. So, why is this promising class of drugs suddenly in the hot seat? At the heart of the issue is an excess of deaths in clinical trials of PI3K inhibitors and the FDA’s concern about their safety profile.

On April 21 of this year, the FDA convened a public Oncologic Drugs Advisory Committee (ODAC) meeting to discuss the agency’s concerns about PI3K inhibitors. The panel voted resoundingly (16 yes votes; 1 abstention) that future approvals of PI3K inhibitors should be supported by randomized data, which would allow for an assessment of overall survival (OS)—an action that makes accelerated approvals less likely and more difficult to obtain in cancers with a long life expectancy.

The panel voted resoundingly (16 yes votes; 1 abstention) that future approvals of PI3K inhibitors should be supported by randomized data, which would allow for an assessment of overall survival (OS)—an action that makes accelerated approvals less likely and more difficult to obtain in cancers with a long life expectancy.

We’ll take you inside this evolving saga. This first installment describes the drug class and what happened at a recent ODAC meeting, with top-line takeaways for drug developers in this field. Subsequent installments will analyze the implications of the panel discussion and the broader regulatory implications of that ODAC meeting and the FDA’s recent actions.

“Not a Typical ODAC Meeting”

The FDA used the April 21 ODAC meeting to zero-in on safety concerns with the class as a whole and to reevaluate the appropriate regulatory approach for future approvals. Nicole Gormley, MD, Director the Division of Hematologic Malignancies, opened up the FDA presentation by first explaining that “this committee meeting is not a typical ODAC where we would discuss the risk-benefit profile of a specific product. But instead, we will discuss the class of PI3K inhibitors as a whole, the unique toxicities that they present, and the best development approach for future drugs in this class.”

This is actually quite unusual—typically, FDA does not ask ODAC panels to provide forward-looking advice for hypothetical future new drug approvals.

Some panelists questioned if it was appropriate to make determinations for an entire drug class on the basis of collective data rather than the individual merits of each drug. Indeed, the one panel member who abstained from voting, Anthony Sung, MD, from Duke, cited this fact as the reason for his abstaining, “I still feel uncomfortable labelling an entire class and requiring that future drugs in that class be supported by randomized data. If the phase 1 data [are] not concerning, then I don’t know if randomized studies should be needed in that case.” While Dr. Gormley assured the panel that flexibility would be applied in specific cases, saying “nobody has a ‘crystal ball’,” the nature of the ODAC and recent agency actions suggests that the FDA plans to apply this advice broadly.

I still feel uncomfortable labelling an entire class and requiring that future drugs in that class be supported by randomized data.

Approved PI3K Inhibitors: Promising efficacy, paired with lingering safety concerns

The Class 1 PI3Ks are master regulators of cell proliferation, growth, survival, motility, and immune cell function. They have long been recognized as one of the most frequently aberrantly activated pathways in cancer, making this a “holy grail” drug target. Certain PI3K isoforms are implicated more strongly in different cancers. PI3Kδ and γ, for example, are preferentially expressed in B lymphocytes and are often constitutively activated in B-cell malignancies.1 Consequently small-molecule PI3K inhibitors with varying levels of selectivity for several PI3K isoforms have been developed, mainly for B-cell malignancies like chronic lymphocytic leukemia (CLL), and indolent non-Hodgkin’s lymphomas (iNHL), including marginal zone lymphoma (MZL) or follicular lymphoma (FL).

Table 1 summarizes the FDA-approved PI3K inhibitors that were the subject of the April 21 ODAC, and the history of FDA approvals for each. As of writing this article, most accelerated approval indications in Table 1, and several new marketing applications for PI3K inhibitors in blood cancer, have been withdrawn (including applications for accelerated approval in MZL/FL for MEI Pharma’s zandelisib (ME-401) and Incyte’s parsaclisib, and most recently, TG Therapeutics’ umbralisib).

Drug Name, (Company) PI3Ki Isoform Selectivity Indication(s) Monotherapy/ Combination Approval History
idelalisib/Zydelig
(Gilead)		 PI3Kδ inhibitor R/R CLL Combination with rituximab 2014, Regular approval
FL/SLL after ≥2 prior systemic therapies Monotherapy 2014, Accelerated approval
2022, Voluntary withdrawal
copanlisib/Aliqopa
(Bayer)		 Pan-PI3K inhibitor FL after ≥2 prior systemic therapies Monotherapy 2017, Accelerated approval
Relapsed iNHL Combination with rituximab 2022, Voluntary withdrawal of marketing application
duvelisib/Copiktra
(Secura Bio)		 Dual PI3Kγ/δ inhibitor CLL/SLL after ≥2 prior systemic therapies Monotherapy 2018, Regular approval
FL after ≥2 prior systemic therapies Monotherapy 2018, Accelerated approval
2021, Voluntary withdrawal
alpelisib/Piqray*
(Novartis)		 PI3Kα inhibitor Advanced breast cancer (PIK3CA-mutated, HR+, HER2–) Combination with fulvestrant 2019, Regular approval
umbralisib/Ukoniq
(TG Therapeutics)		 PI3Kδ inhibitor (also inhibits CK1ε) CLL/SLL, treatment-naive or relapsed Combination with ublituximab 2022, Voluntary withdrawal of marketing application
R/R MZL/FL Monotherapy 2021, Accelerated approval
2022, Voluntary withdrawal

Table 1: Summary of FDA-approved PI3K inhibitors and current status of approvals and new marketing applications for additional indications.

CLL=chronic lymphocytic leukemia; FL=follicular lymphoma; HER2–, human epidermal growth factor receptor-2–negative; HR+, hormone receptor-positive; iNHL=indolent non-Hodgkin’s lymphoma; MZL=marginal zone lymphoma; PI3K=phosphatidylinositol 3-kinase; PIK3CA, phosphatidylinositol-4,5-bisphosphate 3-kinase, catalytic subunit alpha; R/R= relapsed/refractory; SLL, small lymphocytic leukemia. *Because of the FDA’s focus on PI3K inhibitors in blood cancer, the PI3Kα inhibitor, alpelisib, approved for advanced breast cancer in 2019, was not included in recent ODAC discussions and is not discussed in this post.

These approvals validated the promising clinical activity of PI3K inhibitors in blood cancers based on improvements in progression-free survival (PFS) and overall response rates (ORR); nevertheless, the class has been associated with safety issues. Because PI3K regulates the immune response, inhibition of this pathway leads to immune-related adverse events such as transaminitis, pneumonitis, diarrhea/colitis, and rash that are sometimes severe.2 These agents are also associated with an increased risk of infection. This means that adverse events and infectious complications need to be carefully managed by the treating physician.2

The core of FDA’s concern was a pattern suggesting a potential detriment in overall survival (OS) in patients treated with PI3K inhibitors. The FDA presented data at the ODAC showing that in 6, randomized, phase 3 trials for the approved PI3K inhibitors, most demonstrated an OS hazard ratio (HR) >1. A HR >1 means that there were more patients who died on the experimental PI3K inhibitor arm than on the comparator arm. The FDA hypothesized that this pattern could be caused by an increased risk of infection or immune-mediated adverse events or by unidentified long-term effects of PI3K inhibitors, which may negatively affect the efficacy of subsequent therapies.4

The core of FDA’s concern was a pattern suggesting a potential detriment in overall survival (OS) in patients treated with PI3K inhibitors.

Not all PI3K inhibitors have identical safety profiles. To minimize risks, drug companies have developed next-generation PI3K inhibitors, such as umbralisib and duvelisib, with greater selectivity for specific PI3K isoforms. These developments have led to hope in the scientific community that next-generation PI3K inhibitors are “finally coming of age.”5 However, infections and immune-mediated adverse events are still important recognized risks related to the class.

Topline Takeaway: Randomized trial data with an evaluation of OS to support new approvals of PI3K inhibitors

The primary outcome of the April 21 ODAC was the panel’s unanimous vote that randomized trials should be necessary to support future approvals of PI3K inhibitors. Sponsors should anticipate that the ODAC vote will likely translate into regulatory policy. While this does not necessarily affect the regulatory threshold for full approvals (where randomized data has always been required), this decision would make accelerated approvals based on single-arm trials less likely for PI3K inhibitors. Sponsors seeking new approvals for PI3K inhibitors should plan to base their New Drug Applications on randomized clinical trial data and should design clinical trials to include an evaluation of OS. Sponsors should be aware, however, that FDA appears to be looking for an OS hazard ratio of <1.

Sponsors seeking new approvals for PI3K inhibitors should plan to base their New Drug Applications on randomized clinical trial data and should design clinical trials to include an evaluation of OS. Sponsors should be aware, however, that FDA appears to be looking for an OS hazard ratio of <1.

Coming Next: Part 2 — How Should Overall Survival Data Be Evaluated in Blood Cancers?

The rationale for requiring randomized trials specifically for PI3Kis was to allow for an assessment of OS as a safety endpoint. However, assessing OS in patients with indolent blood cancers, who have very long lifespans, can be exceedingly difficult—and the results are not always interpretable. Many panelists questioned the feasibility of assessing OS and how this information should be used in regulatory decision making moving forward.

In Part 2 of this series, ProEd will review in detail the OS data for PI3K inhibitors presented at the April 21 ODAC and the broader regulatory implications of an increased focus on OS as a safety endpoint in patients with indolent blood cancers.

Angela W. Corona, PhD
Scientific Director, ProEd Regulatory

Angela is a Scientific Director for ProEd Regulatory. She is responsible for helping sponsors navigate complex regulatory communications such as FDA advisory committee meetings. She develops clinical and regulatory strategy along with high-quality scientific and medical content across a wide range of therapeutic and drug development areas. Angela received her PhD in Neuroscience from The Ohio State University and completed her postdoctoral training at Case Western Reserve University in Cleveland, Ohio.

 

References

  1. Phillips TJ, Michot JM, Ribrag V. Can next-generation PI3K inhibitors unlock the full potential of the class in patients with B-cell lymphoma? Clin Lymphoma Myeloma Leuk. 2021;21(1):8-20.e3.
  2. Hanlon A, Brander DM. Managing toxicities of phosphatidylinositol-3-kinase (PI3K) inhibitors. Hematology Am Soc Hematol Educ Program. 2020;2020(1):346-356. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7727518/
  3. FDA Presentation, Introductory Comments; Presented by Nicole Gormley. Oncologic Drugs Advisory Committee Meeting. Phosphatidylinositol 3-Kinase (PI3K) Inhibitors in Hematologic Malignancies. April 21, 2022. https://www.fda.gov/media/157837/download
  4. FDA Briefing Document. Oncologic Drugs Advisory Committee Meeting. Phosphatidylinositol 3-Kinase (PI3K) Inhibitors in Hematologic Malignancies. April 21, 2022. https://www.fda.gov/media/157762/download
  5. Vanhaesebroeck B, Perry MWD, Brown JR, André F, Okkenhaug K. PI3K inhibitors are finally coming of age. Nat Rev Drug Discov. 2021;20(10):741-769.

COVID-19 Vaccines: When Will the Pandemic End?

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As Pfizer, Moderna, and other pharma companies prepare to seek emergency authorization for their SARS-CoV-2 vaccines, the FDA has laid out a roadmap designed to ensure appropriate scientific rigor and help engender public trust. That plan was the subject of a special meeting of the Vaccines and Related Biological Products Advisory Committee (VRBPAC) on October 22, 2020, where experts discussed 2 critical FDA guidance documents that provide a blueprint for development and approval of SARS-CoV-2 vaccines. That blueprint is at the center of a massive government effort to quickly and safely speed vaccines to the American public and bring the pandemic to an end.

Members of the VRBPAC, with expertise in infectious disease, epidemiology, and vaccine development, focused on issues around the FDA standards for safety and effectiveness that will support Emergency Use Authorization (EUA) of vaccine candidates. They discussed the need to continue the phase 3, randomized, placebo-controlled trials to completion after an EUA is granted. They considered how the vaccines will be rolled out to the American public, and they raised concerns about whether the public will embrace the vaccines and roll up their sleeves.

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Making Sense of FDA’s Expedited Drug Approval Pathways and Designations – for the Non-Regulatory Professional

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blog header linkedin - FDA Approval v6 blog sizeOne of the fundamental responsibilities of the US Food and Drug Administration (FDA) is to approve effective medicines for people who need them, while upholding high standards for safety. That mission also demands that the FDA work efficiently and not delay approval of life-saving medical advances. Today, the FDA is reviewing applications for approval of new medicines faster than ever, and that’s a welcome change from the status quo 25 years ago. In the era from 1962 (immediately following the thalidomide recall) to the early 1990s, FDA review times for a New Drug Application (NDA) or Biologic License Agreement (BLA) were often measured in years rather than months. In 1993, the standard review time (from NDA or BLA submission to decision) for a new molecular or biologic entity (parlance for a drug not previously approved for any other use) was about 28 months,1 and in some cases, approvals were delayed for many years.

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Can You Predict Whether You Will Face an FDA Advisory Committee?

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blog header linkedin - Prediction Ad Com v5 resizeThe US Food and Drug Administration (FDA) review of drugs, although guided by broad standards, remains individualized. Each drug or drug class faces unique challenges during the FDA review phase – thus no two reviews are exactly the same. Each review division within the FDA has its own approach, and evaluations often differ among the centers. To help understand the review process, the team at ProEd Regulatory sought to learn from the past to inform our future. We reviewed applications submitted to the Center for Drug Evaluation and Research (CDER) data over the last 70 years to see what patterns might emerge. Although the largest proportion of products (drugs and biologics) fails between discovery and Phase 3, an evaluation of applications submitted to the FDA over the last 70 years shows that the vast majority of products that reach the submission stage are ultimately approved (Figure 1).1
predict_fig_1It wasn’t until the Kefauver-Harris Drug Amendments of 1962 that the FDA required sponsors to demonstrate both efficacy and safety of their drugs prior to market access. In the wake of this significant legislation’s impact on drug development, we still see a consistent flow of approved applications and a corresponding subset of new molecular entities (NMEs) (Figure 2).1

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