Differences in drug approval processes of 3 regulatory agencies: a case study of gemtuzumab ozogamicin

Continued cancer drug approvals in Japan and Europe after market withdrawal in the United States: A comparative study of accelerated approvals

Regulatory authorities must balance ensuring evidence of efficacy and safety of new drugs. Various regulatory pathways, such as the accelerated approval program in the United States (US), allow authorities to quickly approve drugs for severely ill patients by granting market authorization based on surrogate end points and pending confirmatory trials. In this cross-sectional study, we considered 23 indications of cancer drugs that received accelerated approval by the US Food and Drug Administration (FDA) but were subsequently withdrawn as of April 2023. Our investigation extended to assessing the regulatory status of these accelerated approvals in the European Union (EU) and Japan, examining relevant regulatory documents and identifying factors contributing to the withdrawal in the United States. Comparing regions, we found that for 52% (12/23) and 30% (7/23) of withdrawn accelerated approvals in the United States, sponsors had also sought marketing authorization from the European Medicines Agency (EMA) and Japan's Pharmaceuticals and Medical Devices Agency (PMDA), respectively. As of the April 30, 2023 study cutoff date, 83% (10/12) of drug-indication pairs remained approved by the EMA, while the PMDA retained 100% (7/7). For these indications, the time from FDA withdrawal until the study cutoff date ranged from 0.23 years to 11.45 years for EMA approvals (median: 1.28 years) and 1.10 years to 11.45 years for PMDA approvals (median: 3.22 years). These findings highlight substantial regulatory discrepancies concerning cancer drugs with unconfirmed benefits. Addressing these discrepancies may involve requiring pharmaceutical companies to confirm clinical benefits using more robust end points and fostering international harmonization in regulators' assessment.

Pharmacovigilance for rare diseases: a bibliometrics and knowledge-map analysis based on web of science

OBJECTIVES

The aims of this paper is to search and explore publications in the field of pharmacovigilance for rare diseases and to visualize general information, research hotspots, frontiers and future trends in the field using the bibliometric tool CiteSpace to provide evidence-based evidence for scholars.

METHODS

We searched the Web of Science Core Collection (WoSCC) for studies related to pharmacovigilance for rare diseases, spanning January 1, 1997-October 25, 2022. CiteSpace software was utilized to discuss countries/regions, institutions, authors, journals, and keywords.

RESULTS

After screening, a total of 599 valid publications were included in this study, with a significant upward trend in the number of publications. These studies were from 68 countries/regions with the United States and the United Kingdom making the largest contributions to the field. 4,806 research scholars from 493 institutions conducted studies on pharmacovigilance for rare diseases. Harvard University and University of California were the top two productive institutions in the research field. He Dian of the Affiliated Hospital of Guizhou Medical University and Peter G.M. Mol of the University of Groningen, The Netherlands, were the two most prolific researchers. The Cochrane Database of Systematic Reviews and the New England Journal of Medicine were the journals with the highest number of articles and co-citation frequency respectively. Clinical trial, therapy and adverse event were the top three most cited keywords.

CONCLUSIONS

Based on keywords co-occurrence analysis, four research topics were identified: orphan drug clinical trials, postmarketing ADR surveillance for orphan drugs, rare diseases and orphan drug management, and diagnosis and treatment of rare diseases. Immune-related adverse reactions and benefit-risk assessment of enzyme replacement therapy were at the forefront of research in this field. Treatment outcomes, early diagnosis and natural history studies of rare diseases may become hotspots for future research.

Curing childhood cancer the "Natural" Way: Nature as the source of chemotherapy agents

For many centuries, products of natural origin from plants, marine, microbes and soil micro-organisms have been studied by numerous researchers across the world to yield many of the chemotherapeutic agents we use in this modern era. There has been a tremendous gain in knowledge from various screening and separating techniques which led to the discovery of biologically active small molecules from natural products. Preclinical studies testing the antitumor activities of these agents against tumor cell lines and xenograft animal models were the gateway to the clinical trials in humans leading to the approval of these agents that are in clinical use today. This review summarizes how various chemotherapeutic agents were discovered from products of natural origin, their preclinical development, and their indications in both pediatric and adult oncology. Many of these natural products have contributed to the very high cure rates of both pediatric leukemias and solid tumors.

Global Landscape of Benefit-Risk Considerations for Medicinal Products: Current State and Future Directions

In the last decade there has been a significant increase in the literature discussing the use of benefit-risk methods in medical product (including devices) development. Government agencies, medical product industry groups, academia, and collaborative consortia have extensively discussed the advantages of structured benefit-risk assessments. However, the abundance of information has not resulted in a consistent way to utilize these findings in medical product development. Guidelines and papers on methods, even though well structured, have not led to a firm consensus on a clear and consistent approach. This paper summarizes the global landscape of benefit-risk considerations for product- or program-level decisions from available literature and regulatory guidance, providing the perspectives of three stakeholder groups-regulators, collaborative groups and consortia, and patients. The paper identifies key themes, potential impact on benefit-risk assessments, and significant future trends.

A critical appraisal of Japan's new drug approval process: a case study of FLT3-ITD inhibitor quizartinib

In the last two decades, simultaneous global development of novel drugs become more common by conducting multiregional clinical trials. However, regulatory authorities of different regions often make different decisions on the approvals of the same new drugs. We would like to discuss the appropriateness of Japanese regulatory approach through a case study of quizartinib, a novel anti-leukemia drug developed in Japan. The pivotal clinical trial "QuANTUM-R" conducted in 19 countries showed a modest increase in median overall survival with quizartinib than the conventional chemotherapy. However, because several critical defects in this trial were pointed out by the United States Food and Drug Administration (US FDA) and the European Medicines Agency (EMA), quizartinib has not been approved in the US and Europe to date. On the contrary, the regulatory authority of Japan gave a notice of approval to quizartinib as a "standard of care", and the country becomes the sole country that granted market authorization. In our paper, we provide more detailed discussion about the methodology for scientific evaluation of the new drug.

Mechanisms contributing to ado-trastuzumab emtansine-induced toxicities: a gateway to better understanding of ADC-associated toxicities

In order to improve the safety of novel therapeutic drugs, better understanding of the mechanisms of action is important. Ado-trastuzumab emtansine (also known as T-DM1) is an antibody-drug conjugate (ADC) approved for the treatment of HER2-positive breast cancer. While the treatment with T-DM1 results in significant efficacy in the selected patient population, nonetheless, there are concerns with side effects such as thrombocytopenia and hepatotoxicity. While current understanding of the mechanism of T-DM1-mediated side effects is still incomplete, there have been several reports of HER2-dependent and/or -independent mechanisms that could be associated with the T-DM1-induced adverse events. This review highlights the importance of HER2-independent mechanism of T-DM1 to induce hepatotoxicity, which offers a new insight into a role for CKAP5 in the overall maytansinoid-based ADC (DM1 and DM4)-mediated cytotoxicity. This discovery provides a molecular basis for T-DM1-induced off-target toxicity and opens a new avenue for developing the next generation of ADCs.

Antibody-Drug Conjugates: The New Frontier of Chemotherapy

In recent years, antibody-drug conjugates (ADCs) have become promising antitumor agents to be used as one of the tools in personalized cancer medicine. ADCs are comprised of a drug with cytotoxic activity cross-linked to a monoclonal antibody, targeting antigens expressed at higher levels on tumor cells than on normal cells. By providing a selective targeting mechanism for cytotoxic drugs, ADCs improve the therapeutic index in clinical practice. In this review, the chemistry of ADC linker conjugation together with strategies adopted to improve antibody tolerability (by reducing antigenicity) are examined, with particular attention to ADCs approved by the regulatory agencies (the U.S. Food and Drug Administration (FDA) and the European Medicines Agency (EMA)) for treating cancer patients. Recent developments in engineering Immunoglobulin (Ig) genes and antibody humanization have greatly reduced some of the problems of the first generation of ADCs, beset by problems, such as random coupling of the payload and immunogenicity of the antibody. ADC development and clinical use is a fast, evolving area, and will likely prove an important modality for the treatment of cancer in the near future.

Effect and safety of gemtuzumab ozogamicin for the treatment of patients with acute myeloid leukaemia: a systematic review protocol

INTRODUCTION

Acute myeloid leukaemia (AML) is a type of cancer in which the bone marrow makes abnormal myeloblasts (a type of white blood cell), red blood cells or platelets. Gemtuzumab ozogamicin (GO) holds promise as a new agent that also could be efficacious in newly diagnosed AML with acceptable toxicity. This paper describes the design of a protocol to conduct a systematic review of published studies assessing GO for the treatment of AML.

METHOD AND ANALYSIS

We will conduct a systematic review of randomised controlled trials that investigate the effect and safety of GO for the treatment of patients with AML. We will search for any eligible articles from selected electronic databases. We will follow the Preferred Reporting Items for Systematic reviews and Meta-Analysis for study selection and reporting. We will use The Cochrane Handbook for Systematic Reviews of Interventions and Meta-Analysis as guidance to select eligible studies. All data will be extracted using a standardised data extraction form.

ETHICS AND DISSEMINATION

There was no patient involved in this study, therefore no ethical consideration is needed. The findings of this study will be disseminated in a peer-reviewed journal and any relevant conference presentation.

PROSPERO REGISTRATION NUMBER

CRD42019123286.

ADCs, as Novel Revolutionary Weapons for Providing a Step Forward in Targeted Therapy of Malignancies

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Antibody drug conjugates (ADCs), as potent pharmaceutical trojan horses for cancer treatment, provide superior efficacy and specific targeting along with low risk of adverse reactions compared to traditional chemotherapeutics. In fact, the development of these agents combines the selective targeting capability of monoclonal antibody (mAb) with high cytotoxicity of chemotherapeutics for controlling the neoplastic mass growth. Different ADCs (more than 60 ADCs) in preclinical and clinical trials were introduced in this novel pharmaceutical field. Various design-based factors must be taken into account for improving the functionality of ADC technology, including selection of appropriate target antigen and high binding affinity of fragment (miniaturized ADCs) or full mAbs (preferentially use of humanized or fully human antibodies compared to murine and chimeric ones), use of bispecific antibodies for dual targeting effect, linker engineering and conjugation method efficacy to obtain more controlled drug to antibody ratio (DAR). Challenging issues affecting therapeutic efficacy and safety of ADCs, including bystander effect, on- and off-target toxicities, multi drug resistance (MDR) are also addressed. 4 FDA-approved ADCs in the market, including ADCETRIS ®, MYLOTARG®, BESPONSA ®, KADCYLA®. The goal of the current review is to evaluate the key parameters affecting ADCs development.

To what degree are review outcomes aligned for new active substances (NASs) between the European Medicines Agency and the US Food and Drug Administration? A comparison based on publicly available information for NASs initially approved in the time period 2014 to 2016

OBJECTIVE

To compare review outcome alignment between European Medicines Agency (EMA) and US Food and Drug Administration (FDA) for medicines approved by both agencies in the time period 2014-2016.

DESIGN

Using publicly available information from FDA and EMA websites, new active substances (NASs) approved by each agency from 2014 to 2016 were identified and their characteristics assessed. Divergences in regulatory outcomes for simultaneous (within 91 days) submissions to both agencies were identified and then examined for use of facilitated regulatory pathways and orphan designations; submitted versus approved indications; and approval times.

RESULTS

In 2014-2016, 115 NASs were approved by EMA or FDA or both; 74/115 were new chemical entities and 41 new biological/biotechnology entities; 82/115 were approved by both agencies, 24 only by FDA and nine only by EMA. Simultaneous submission occurred for 52/115; 13/52 received expedited review by both agencies and 18 only by FDA; 8/52 received conditional approval from both agencies, 2/52 only from FDA and 1/52 only from EMA; 17/52 were designated as orphans by both agencies and 10/52 by FDA only; 31/52 indications were approved as submitted and 21 changed by EMA and 29/46 were approved as submitted (six not assessed) and 17/46 changed by FDA. Median FDA review timelines were 319 days compared with 409 days for EMA.

CONCLUSIONS

There was general agreement in EMA / FDA conditional approvals. FDA used expedited pathways and orphan designation more often than EMA, suggesting stricter EMA criteria or definitions for these designations or less flexible processes. Despite consistency in submitted indications, there was lack of concordance in approved indications, which should be further investigated. FDA review times are faster because of a wider range of expedited pathways and the two-step EMA process; this may change with recent revisions to EMA accelerated assessment guidelines and the launch of Priority Medicines.

The Latest Research and Development into the Antibody-Drug Conjugate, [fam-] Trastuzumab Deruxtecan (DS-8201a), for HER2 Cancer Therapy

A major limitation of traditional chemotherapy for cancer is dose-limiting toxicity, caused by the exposure of non-tumor cells to cytotoxic agents. Use of molecular targeted drugs, such as specific kinase inhibitors and monoclonal antibodies, is a possible solution to overcome this limitation and has achieved clinical success so far. Use of an antibody-drug conjugate (ADC) is a rational strategy for improving efficacy and reducing systemic adverse events. ADCs use antibodies selectively to deliver a potent cytotoxic agent to tumor cells, thus drastically improving the therapeutic index of chemotherapeutic agents. Lessons learned from clinical failure of early ADCs during the 1980s to 90s have recently led to improvements in ADC technology, and resulted in the approval of four novel ADCs. Nonetheless, further advances in ADC technology are still required to streamline their clinical efficacy and reduce toxicity. [fam-] Trastuzumab deruxtecan (DS-8201a) is a next-generation ADC that satisfies these requirements based on currently available evidence. DS-8201a has several innovative features; a highly potent novel payload with a high drug-to-antibody ratio, good homogeneity, a tumor-selective cleavable linker, stable linker-payload in circulation, and a short systemic half-life cytotoxic agent in vivo; the released cytotoxic payload could exert a bystander effect. With respect to its preclinical profiles, DS-8201a could provide a valuable therapy with a great potential against HER2-expressing cancers in clinical settings. In a phase I trial, DS-8201a showed acceptable safety profiles with potential therapeutic efficacy, with the wide therapeutic index.

How Does "Regulatory Practice" Create Discrepancies in Drug Label Information Between Asian and Western Countries? Different Label Information for Direct Oral Anticoagulants Approved in the United States, Europe, Korea, and Japan

Globalization of the pharmaceutical industry has continued over the past few decades, and various regulatory authorities have put considerable effort into harmonizing and standardizing drug regulations. However, the regulatory practices of each regulatory authority, in addition to local differences in ethnic, social, and cultural backgrounds, create discrepancies in risk/benefit assessments, regulatory decisions, and drug label information in various countries. This study examines discrepancies in the label information for direct oral anticoagulants approved in the US, Europe, Korea, and Japan and reviews the causes of those discrepancies, focusing on regulatory practices. Although the label information for each direct oral anticoagulant in all 4 regions was supported by the same global, pivotal clinical data, it differed depending on regulatory authorities' judgments about the risk/benefit balance, which were based on their own requirements, regulations, perspectives on making regulatory decisions, and regulatory approval experiences, in addition to their review of the scientific data. In particular, the Korean Ministry of Food and Drug Safety and Japanese Pharmaceuticals and Medical Devices Agency have taken a comparatively conservative stance, with more emphasis on safety than on efficacy compared with regulatory authorities in western countries, because of the double threshold in their regulatory practice. Our findings suggest that drug label information in various regions will not be equal as long as differences in regulatory practice and non-regulatory factors exist among regulatory authorities. Also, those differences should be considered in order to streamline global drug discovery, development, and approval.

Gemtuzumab ozogamicin in acute myeloid leukemia

CD33 is variably expressed on leukemia blasts in almost all patients with acute myeloid leukemia (AML) and possibly leukemia stem cells in some. Efforts to target CD33 therapeutically have focused on gemtuzumab ozogamicin (GO; Mylotarg), an antibody-drug conjugate delivering a DNA-damaging calicheamicin derivative. GO is most effective in acute promyelocytic leukemia but induces remissions in other AML types and received accelerated approval in the US in 2000. However, because a large follow-up study showed no survival improvement and increased early deaths the drug manufacturer voluntarily withdrew the US New Drug Application in 2010. More recently, a meta-analysis of data from several trials reported better survival in adults with favorable- and intermediate-risk cytogenetics but not adverse-risk AML randomized to receive GO along with intensive induction chemotherapy. As a result, GO is being re-evaluated by regulatory agencies. Responses to GO are diverse and predictive biological response markers are needed. Besides cytogenetic risk, ATP-binding cassette transporter activity and possibly CD33 display on AML blasts may predict response, but established clinical assays and prospective validation are lacking. Single-nucleotide polymorphisms in CD33 may also be predictive, most notably rs12459419 where the minor T-allele leads to decreased display of full-length CD33 and preferential translation of a splice variant not recognized by GO. Data from retrospective analyses suggest only patients with the rs12459419 CC genotype may benefit from GO therapy but confirmation is needed. Most important may be markers for AML cell sensitivity to calicheamicin, which varies over 100 000-fold, but useful assays are unavailable. Novel CD33-targeted drugs may overcome some of GO's limitations but it is currently unknown whether such drugs will be more effective in patients benefitting from GO and/or improve outcomes in patients not benefitting from GO, and what the supportive care requirements will be to enable their safe use.

Extending the market exclusivity of therapeutic antibodies through dosage patents

Dosage patents are one way to extend the market exclusivity of an approved drug beyond the lifetime of the patent that protects the drug as such. Dosage patents may help to compensate the applicant for the long period where the active pharmaceutical ingredient as such is already under patent prosecution, but not on the market yet, due to lengthy development and approval procedures. This situation erodes part of the time the drug is marketed under patent protection. Dosage patents filed at a later date can provide remedy for this problem. Examples of successful and unsuccesful attempts, and the reasons for the respective outcomes, are provided in this article.

Ado-Trastuzumab Emtansine Targets Hepatocytes Via Human Epidermal Growth Factor Receptor 2 to Induce Hepatotoxicity

Ado-trastuzumab emtansine (T-DM1) is an antibody-drug conjugate (ADC) approved for the treatment of HER2-positive metastatic breast cancer. It consists of trastuzumab, a humanized mAb directed against HER2, and a microtubule inhibitor, DM1, conjugated to trastuzumab via a thioether linker. Hepatotoxicity is one of the serious adverse events associated with T-DM1 therapy. Mechanisms underlying T-DM1-induced hepatotoxicity remain elusive. Here, we use hepatocytes and mouse models to investigate the mechanisms of T-DM1-induced hepatotoxicity. We show that T-DM1 is internalized upon binding to cell surface HER2 and is colocalized with LAMP1, resulting in DM1-associated cytotoxicity, including disorganized microtubules, nuclear fragmentation/multiple nuclei, and cell growth inhibition. We further demonstrate that T-DM1 treatment significantly increases the serum levels of aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase in mice and induces inflammation and necrosis in liver tissues, and that T-DM1-induced hepatotoxicity is dose dependent. Moreover, the gene expression of TNFα in liver tissues is significantly increased in mice treated with T-DM1 as compared with those treated with trastuzumab or vehicle. We propose that T-DM1-induced upregulation of TNFα enhances the liver injury that may be initially caused by DM1-mediated intracellular damage. Our proposal is underscored by the fact that T-DM1 induces the outer mitochondrial membrane rupture, a typical morphologic change in the mitochondrial-dependent apoptosis, and mitochondrial membrane potential dysfunction. Our work provides mechanistic insights into T-DM1-induced hepatotoxicity, which may yield novel strategies to manage liver injury induced by T-DM1 or other ADCs.

Priority review drugs approved by the FDA and the EMA: time for international regulatory harmonization of pharmaceuticals?

INTRODUCTION

The US Food and Drug Administration (FDA) priority review process applies to a drug that is considered a significant improvement over the available alternatives. The European Medicines Agency (EMA) accelerated approval applies to a product that is of major public health interest. This study assessed differences in the characteristics of priority review new molecular entities and new therapeutic biologic products approved by the FDA and the EMA.

METHODS

This study includes regulatory information on drug applications, approvals, indications, and orphan designations of all priority review drugs approved by the FDA and the EMA in the period 1999-2011. Descriptive statistics, t-tests, and chi-squared and Wilcoxon tests were performed.

RESULTS

Overall, 100 FDA priority review new molecular entities and new therapeutic biologics were approved by both agencies; 87.0% of the products were first approved by the FDA. The average FDA review time (9.2 ± 8.4 months) was significantly lower than the EMA average review time (14.6 ± 4.0 months) (p < 0.0001). The FDA and the EMA granted orphan designation to 43.0% and 33.0%, respectively, of the applications. There were differences in the administration route (1.0% of all products), dosage (8.0%), strength (23%), posology (51.0%), indications (30.0%), restrictions of use (52.0%), limitations of use (19.0%), and outcomes limitations (28.0%) approved by both regulatory agencies.

CONCLUSION

Significant differences exist in the characteristics of the priority review drugs approved by the FDA and the EMA. Harmonization of the US and European regulatory frameworks may facilitate timely approval of pharmaceutical products.

A perspective on the benefit-risk assessment for new and emerging pharmaceuticals in Japan

The universal health care system in Japan is facing a historical turning point as a result of the increasing fiscal burden, rapidly aging society, and a decreasing population. To understand the challenges and opportunities in the Japanese pharmaceutical market, which occupies one tenth of the global share, this review highlights several issues related to the benefit-risk assessment that is unique to the modern Japanese society: 1) regulatory system for new drug development; 2) health hazards related to pharmaceuticals ("Yakugai" in Japanese); 3) drug lag; 4) problems and controversies in the vaccination policy; and 5) clinical study misconduct. The regulatory process places a significant importance on Japanese data collection regardless of data accumulation from other countries. Because Yakugai has repeatedly caused tragedies and social disputes historically, the regulatory judgments generally tend to be more prudential when safety concerns are raised for new and emerging pharmaceuticals. Such a regulatory system has caused more than several years of approval delays compared to delays in other countries. The problem of drug lag still lingers on despite several regulatory system revisions, while the solution is incompatible with the elimination of Yakugai because the lag potentially reduces the risk of unpredictable adverse events. The Japanese vaccination policy has also received a lot of criticism, and needs improvements so that the decision-making process can be more transparent and scientifically based. Additionally, repeated clinical study misconduct damaged the reputation of Japanese clinical studies with unnecessary defrayment in health insurance; therefore, the medical community must change its inappropriate relationship with the industry. The problems surrounding pharmaceuticals are related to centralized, strict drug pricing control under the universal health coverage. Although the current government attempts to facilitate innovative research and development of novel therapeutics in Japan, further reforms should be explored for patients who need new and emerging pharmaceuticals.

Does technique matter; a pilot study exploring weighting techniques for a multi-criteria decision support framework

Background

There is an increased interest in the use of multi-criteria decision analysis (MCDA) to support regulatory and reimbursement decision making. The EVIDEM framework was developed to provide pragmatic multi-criteria decision support in health care, to estimate the value of healthcare interventions, and to aid in priority-setting. The objectives of this study were to test 1) the influence of different weighting techniques on the overall outcome of an MCDA exercise, 2) the discriminative power in weighting different criteria of such techniques, and 3) whether different techniques result in similar weights in weighting the criteria set proposed by the EVIDEM framework.

Methods

A sample of 60 Dutch and Canadian students participated in the study. Each student used an online survey to provide weights for 14 criteria with two different techniques: a five-point rating scale and one of the following techniques selected randomly: ranking, point allocation, pairwise comparison and best worst scaling.

Results

The results of this study indicate that there is no effect of differences in weights on value estimates at the group level. On an individual level, considerable differences in criteria weights and rank order occur as a result of the weight elicitation method used, and the ability of different techniques to discriminate in criteria importance. Of the five techniques tested, the pair-wise comparison of criteria has the highest ability to discriminate in weights when fourteen criteria are compared.

Conclusions

When weights are intended to support group decisions, the choice of elicitation technique has negligible impact on criteria weights and the overall value of an innovation. However, when weights are used to support individual decisions, the choice of elicitation technique influences outcome and studies that use dissimilar techniques cannot be easily compared. Weight elicitation through pairwise comparison of criteria is preferred when taking into account its superior ability to discriminate between criteria and respondents’ preferences.

Electronic supplementary material

The online version of this article (doi:10.1186/1478-7547-12-22) contains supplementary material, which is available to authorized users.

Targeting CD22 in B-cell malignancies: current status and clinical outlook

CD22 is a B-cell-specific transmembrane glycoprotein found on the surface of most B cells; it modulates B-cell function, survival and apoptosis. CD22 has emerged as an ideal target for monoclonal antibody (mAb)-based therapy of B-cell malignancies including most lymphomas and many leukemias. Epratuzumab, an anti-CD22 mAb, has been developed in various forms, including as an unlabeled (naked) mAb, as a radioimmunotherapeutic, as an antibody drug conjugate (ADC), and as a vehicle for CD22-targeted nanoparticles. While clinical trials with unlabeled epratuzumab have demonstrated modest results, its combination with rituximab in phase II studies has been more encouraging. Based on the potential for CD22 to become internalized, CD22-targeted constructs carrying radioisotopes or toxins have generated promising results. Radioimmunotherapy, utilizing ⁹⁰Y-labeled epratuzumab, was shown to be highly effective in patients with follicular lymphoma, generating a complete response (CR) rate of 92 % and progression-free survival of more than 2 years. ADC therapy is a promising therapeutic approach to B-cell malignancies which includes the direct conjugation of mAbs with cytotoxic agents. Phase II studies of inotuzumab ozogamicin, an ADC which combines anti-CD22 mAb with calicheamicin, an enediyne antibiotic which mediates apoptosis, in patients with acute lymphoblastic leukemia have produced an overall response rate (ORR) of greater than 50 % in treatment-refractory patients. Phase I trials of moxetumomab pasudotox, an ADC which combines anti-CD22 with PE38, a fragment of Pseudomonas exotoxin A, have been completed in hairy cell leukemia with a ORR of 86 %. Finally, a review of CD22-targeted nanoparticles, that include a doxorubicin-containing lipid complex that uses synthetic high-affinity CD22 ligand mimetics as well as anti-CD22 mAb-coated pegylated liposomas doxorubin (PLD), has demonstrated promising results in pre-clinical models of human lymphoma. Moreover, novel anti-CD22 mAb that block CD22 ligand binding as well as second generation ADC that utilize biodegradable linkers and more potent toxins hold great hope for the future of CD22-targeted therapeutics that may translate into better outcomes for patients with CD22-positive malignancies.

Natural product and natural product derived drugs in clinical trials

The 25 Natural Product (NP)-derived drugs launched since 2008 and the 100 NP-derived compounds and 33 Antibody Drug Conjugates (ADCs) in clinical trials or in registration at the end of 2013 are reviewed.