REVIEW EDITORIAL For reprint orders, please contact: [email protected]
RNA interference in the clinics: where are we standing now?
“...RNA interference may successfully treat human diseases.”
Rishi Wagle1, Masahisa Ohtsuka1, Hui Ling1 & Martin Pichler*,1 Over the last decade, the field of cancer therapy and the mode of action of approved cancer drugs have dramatically changed across the globe. The struggle against cancer in clinical trials shifted from the testing of cytotoxic ‘classical’ chemotherapeutic drugs toward agents with clearly defined molecular targets [1] . A deeper understanding of the underlying molecular and cellular mechanisms in cancer cells including cancer stem cells, miRNAs and circulating tumor DNA [2,3] , which has been exponentially generated within the last 50 years, enabled the development of new drugs. This new class of targeted agents can essentially be divided into two groups of cancer therapeutics: small orally available molecules directed against intracellular (multiple) tyrosine kinases or mTOR pathway and ‘big’ monoclonal antibodies that are mainly directed against extracellular targets including membranous and soluble proteins [4] . Besides that evolution, other potentially targetable biological structures and mechanisms have been identified. One of them, the RNA interference (RNAi), an endogenous cellular mechanism for controlling gene expression that can be mediated by small interfering RNA
(siRNA), is of great promise [5] . SiRNA is a small dsRNA that, when associating with its complementary RNA strand, binds to the RNA-induced silencing complex and thereafter mediates target mRNA cleavage and degradation through a catalytic process involving the Argonaute 2 endonuclease [5] . Since their discovery almost two decades ago, thousands of in vitro and in vivo studies have been performed, largely supporting this technology as a potential cancer therapeutic strategy. Despite all of the hype, the road to reality is long and sometimes, celebrated rising stars fail to succeed in the long term. With this critical consideration in mind, we can now ask: where are we now in the year (2014) in the clinic with RNA cancer therapeutics? Despite the extraordinary use of siRNA technology in in vitro and in vivo experimental models, one has to be surprised when searching the list of available reports for clinical trials using such agents for cancer patients. The first data published about nonvirally delivered synthetic siRNA came from a case report, where a female patient with imatinib-resistant chronic myeloid leukemia (after autologous bone marrow transplantation) received a bcr-abl
KEYWORDS
• cancer • efficacy • RNA interference • safety • therapy
“The struggle against cancer in
clinical trials shifted from the testing of cytotoxic ‘classical’ chemotherapeutic drugs toward agents with clearly defined molecular targets.”
Department of Experimental Therapeutics, The University of Texas MD Anderson Cancer Center, Houston, TX 77054, USA *Author for correspondence: [email protected] 1
10.2217/FON.14.243 © 2015 Future Medicine Ltd
Future Oncol. (2015) 11(2), 185–187
part of
ISSN 1479-6694
185
Editorial Wagle, Ohtsuka, Ling & Pichler oncogene directed siRNA. The authors reported a remarkable inhibition of the overexpressed bcrabl oncogene and an increased apoptosis rate of chronic myeloid leukemia cells [6] . Intriguingly, this first-human in vivo siRNA application was well tolerated without any clinically relevant adverse events (AEs) reported [6] . Also important to consider, the lack of major adverse effects makes this therapy different from currently used ones and highlights the potential impact such agents can have. However, one major reason for the unsolved problem for the use of this technology in humans arrives in the delivery stage. The siRNA-transport complex should selectively target the altered molecules in cancer cells, but should avoid adverse effects in healthy noncancerous cells. Nanoparticle formulations are currently favored and tested in many preclinical models. One of these formulations, a linear, cyclodextrin-based polymer with a human transferrin protein (TF) targeting ligand and siRNA designed to reduce the expression of the well-known protein coding gene RRM2 (clinical version of this agent is denoted as CALAA-01), has been reported as the first in-human Phase I clinical trial involving the systemic administration of siRNA to patients with solid cancers [7] . In this first report, the authors demonstrated their confirmation of up-take of nanoparticles and target-site effects of the specific siRNA. They obtained tumor biopsies from three melanoma patients before and after treatment and showed the presence of intracellularly localized nanoparticles in amounts that correlated with dose levels of the nanoparticles administered. Interestingly, they also found a reduction of the specific messenger RNA and protein levels of RRM2, and confirmed the cleavage of the mRNA by detection of mRNA fragments [7] . This report was a proof-of principle that the concept of siRNA-targeted gene silencing is also working in humans. Very recently, the authors reported the final results of this Phase I clinical trial [8] . Overall, 24 patients with different types of solid cancers have been included. There were some AEs reported including treatment-related AEs of any grade with incidence in greater than 15% of patients: fatigue (n = 12), chills (n = 12) and References 1
186
Cook N, Hansen AR, Siu LL, Abdul Razak AR. Early phase clinical trials to identify optimal dosing and safety. Mol. Oncol. doi: 10.1016/j.molonc.2014.07.025 (2014) (Epub ahead of print).
fever (n = 10). Grade 3/4-related AEs occurring in multiple patients included lymphopenia (n = 3) and fatigue (n = 2). Grade 3/4-related AEs during CALAA-01 infusions included hypersensitivity, ischemic colitis, diarrhea and fever (n = 1 each). Summarizing these AEs, there seems to be room for further improvement of the tolerability and better understanding of siRNA-delivery systems. The true value of the efficiency of CALAA-01 has to be clarified in further clinical trial. Recently, another published clinical Phase I study used a lipid nanoparticle formulation for siRNA delivery [9] . In this study, Tabernero et al. reported a trial of ALN-VSP, a lipid nanoparticle formulation of siRNAs targeting the VEGF and the kinesin spindle protein, in patients with advanced cancer and liver metastases. This study could also detect the drug in tumor biopsies, confirming siRNAmediated mRNA cleavage in the liver and antitumor activity, including complete regression of liver metastases in a patient with advanced endometrial cancer. The biweekly intravenous administration of ALN-VSP was safe and well-tolerated. The concept of delivering two or more siRNAs in one delivery system to enhance the efficiency of targeting two or more pharmacological targets appears to be promising. Interestingly, a recently published pre-clinical ovarian cancer study discussed the combination of siRNA and miRNA in one delivery system to synergize the therapeutic efficiency of both molecules [10] . Taken together, all of these studies indicate that RNA interference may successfully treat human diseases. However, many obstacles must be surpassed before such agents might enter the clinics. Financial & competing interests disclosure The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties. No writing assistance was utilized in the production of this manuscript.
2
Heitzer E, Auer M, Hoffmann EM et al. Establishment of tumor-specific copy number alterations from plasma DNA of patients with cancer. Int. J. Cancer 133, 346–356 (2013).
3
Schwarzenbacher D, Balic M, Pichler M. The role of microRNAs in breast cancer stem cells. Int. J. Mol. Sci. 14, 14712–14723 (2013).
Future Oncol. (2015) 11(2)
4
Kasper S, Schuler M. Targeted therapies in gastroesophageal cancer. Eur. J. Cancer 50, 1247–1258 (2014).
5
Moss EG. RNA interference: it’s a small RNA world. Curr. Biol. 11, R772–R775 (2001).
future science group
RNA interference in the clinics: where are we standing now? 6
7
Koldehoff M, Steckel NK, Beelen DW, Elmaagacli AH. Therapeutic application of small interfering RNA directed against bcr-abl transcripts to a patient with imatinib-resistant chronic myeloid leukaemia. Clin. Exp. Med. 7, 47–55 (2007). Davis ME, Zuckerman JE, Choi CH et al. Evidence of RNAi in humans from systemically administered siRNA via targeted
future science group
nanoparticles. Nature 464, 1067–1070 (2010). 8
Zuckerman JE, Gritli I, Tolcher A et al. Correlating animal and human Phase Ia/Ib clinical data with CALAA-01, a targeted, polymer-based nanoparticle containing siRNA. Proc. Natl Acad. Sci. USA 111, 11449–11454 (2014).
9
Editorial
Tabernero J, Shapiro GI, LoRusso PM et al. First-in-humans trial of an RNA interference therapeutic targeting VEGF and KSP in cancer patients with liver involvement. Cancer Discov. 3, 406–417 (2013).
10 Nishimura M, Jung EJ, Shah MY et al.
Therapeutic synergy between microRNA and siRNA in ovarian cancer treatment. Cancer Discov. 3m 1302–1315 (2013).
www.futuremedicine.com
187
RNA interference in the clinics: where are we standing now?
“...RNA interference may successfully treat human diseases.”
Rishi Wagle1, Masahisa Ohtsuka1, Hui Ling1 & Martin Pichler*,1 Over the last decade, the field of cancer therapy and the mode of action of approved cancer drugs have dramatically changed across the globe. The struggle against cancer in clinical trials shifted from the testing of cytotoxic ‘classical’ chemotherapeutic drugs toward agents with clearly defined molecular targets [1] . A deeper understanding of the underlying molecular and cellular mechanisms in cancer cells including cancer stem cells, miRNAs and circulating tumor DNA [2,3] , which has been exponentially generated within the last 50 years, enabled the development of new drugs. This new class of targeted agents can essentially be divided into two groups of cancer therapeutics: small orally available molecules directed against intracellular (multiple) tyrosine kinases or mTOR pathway and ‘big’ monoclonal antibodies that are mainly directed against extracellular targets including membranous and soluble proteins [4] . Besides that evolution, other potentially targetable biological structures and mechanisms have been identified. One of them, the RNA interference (RNAi), an endogenous cellular mechanism for controlling gene expression that can be mediated by small interfering RNA
(siRNA), is of great promise [5] . SiRNA is a small dsRNA that, when associating with its complementary RNA strand, binds to the RNA-induced silencing complex and thereafter mediates target mRNA cleavage and degradation through a catalytic process involving the Argonaute 2 endonuclease [5] . Since their discovery almost two decades ago, thousands of in vitro and in vivo studies have been performed, largely supporting this technology as a potential cancer therapeutic strategy. Despite all of the hype, the road to reality is long and sometimes, celebrated rising stars fail to succeed in the long term. With this critical consideration in mind, we can now ask: where are we now in the year (2014) in the clinic with RNA cancer therapeutics? Despite the extraordinary use of siRNA technology in in vitro and in vivo experimental models, one has to be surprised when searching the list of available reports for clinical trials using such agents for cancer patients. The first data published about nonvirally delivered synthetic siRNA came from a case report, where a female patient with imatinib-resistant chronic myeloid leukemia (after autologous bone marrow transplantation) received a bcr-abl
KEYWORDS
• cancer • efficacy • RNA interference • safety • therapy
“The struggle against cancer in
clinical trials shifted from the testing of cytotoxic ‘classical’ chemotherapeutic drugs toward agents with clearly defined molecular targets.”
Department of Experimental Therapeutics, The University of Texas MD Anderson Cancer Center, Houston, TX 77054, USA *Author for correspondence: [email protected] 1
10.2217/FON.14.243 © 2015 Future Medicine Ltd
Future Oncol. (2015) 11(2), 185–187
part of
ISSN 1479-6694
185
Editorial Wagle, Ohtsuka, Ling & Pichler oncogene directed siRNA. The authors reported a remarkable inhibition of the overexpressed bcrabl oncogene and an increased apoptosis rate of chronic myeloid leukemia cells [6] . Intriguingly, this first-human in vivo siRNA application was well tolerated without any clinically relevant adverse events (AEs) reported [6] . Also important to consider, the lack of major adverse effects makes this therapy different from currently used ones and highlights the potential impact such agents can have. However, one major reason for the unsolved problem for the use of this technology in humans arrives in the delivery stage. The siRNA-transport complex should selectively target the altered molecules in cancer cells, but should avoid adverse effects in healthy noncancerous cells. Nanoparticle formulations are currently favored and tested in many preclinical models. One of these formulations, a linear, cyclodextrin-based polymer with a human transferrin protein (TF) targeting ligand and siRNA designed to reduce the expression of the well-known protein coding gene RRM2 (clinical version of this agent is denoted as CALAA-01), has been reported as the first in-human Phase I clinical trial involving the systemic administration of siRNA to patients with solid cancers [7] . In this first report, the authors demonstrated their confirmation of up-take of nanoparticles and target-site effects of the specific siRNA. They obtained tumor biopsies from three melanoma patients before and after treatment and showed the presence of intracellularly localized nanoparticles in amounts that correlated with dose levels of the nanoparticles administered. Interestingly, they also found a reduction of the specific messenger RNA and protein levels of RRM2, and confirmed the cleavage of the mRNA by detection of mRNA fragments [7] . This report was a proof-of principle that the concept of siRNA-targeted gene silencing is also working in humans. Very recently, the authors reported the final results of this Phase I clinical trial [8] . Overall, 24 patients with different types of solid cancers have been included. There were some AEs reported including treatment-related AEs of any grade with incidence in greater than 15% of patients: fatigue (n = 12), chills (n = 12) and References 1
186
Cook N, Hansen AR, Siu LL, Abdul Razak AR. Early phase clinical trials to identify optimal dosing and safety. Mol. Oncol. doi: 10.1016/j.molonc.2014.07.025 (2014) (Epub ahead of print).
fever (n = 10). Grade 3/4-related AEs occurring in multiple patients included lymphopenia (n = 3) and fatigue (n = 2). Grade 3/4-related AEs during CALAA-01 infusions included hypersensitivity, ischemic colitis, diarrhea and fever (n = 1 each). Summarizing these AEs, there seems to be room for further improvement of the tolerability and better understanding of siRNA-delivery systems. The true value of the efficiency of CALAA-01 has to be clarified in further clinical trial. Recently, another published clinical Phase I study used a lipid nanoparticle formulation for siRNA delivery [9] . In this study, Tabernero et al. reported a trial of ALN-VSP, a lipid nanoparticle formulation of siRNAs targeting the VEGF and the kinesin spindle protein, in patients with advanced cancer and liver metastases. This study could also detect the drug in tumor biopsies, confirming siRNAmediated mRNA cleavage in the liver and antitumor activity, including complete regression of liver metastases in a patient with advanced endometrial cancer. The biweekly intravenous administration of ALN-VSP was safe and well-tolerated. The concept of delivering two or more siRNAs in one delivery system to enhance the efficiency of targeting two or more pharmacological targets appears to be promising. Interestingly, a recently published pre-clinical ovarian cancer study discussed the combination of siRNA and miRNA in one delivery system to synergize the therapeutic efficiency of both molecules [10] . Taken together, all of these studies indicate that RNA interference may successfully treat human diseases. However, many obstacles must be surpassed before such agents might enter the clinics. Financial & competing interests disclosure The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties. No writing assistance was utilized in the production of this manuscript.
2
Heitzer E, Auer M, Hoffmann EM et al. Establishment of tumor-specific copy number alterations from plasma DNA of patients with cancer. Int. J. Cancer 133, 346–356 (2013).
3
Schwarzenbacher D, Balic M, Pichler M. The role of microRNAs in breast cancer stem cells. Int. J. Mol. Sci. 14, 14712–14723 (2013).
Future Oncol. (2015) 11(2)
4
Kasper S, Schuler M. Targeted therapies in gastroesophageal cancer. Eur. J. Cancer 50, 1247–1258 (2014).
5
Moss EG. RNA interference: it’s a small RNA world. Curr. Biol. 11, R772–R775 (2001).
future science group
RNA interference in the clinics: where are we standing now? 6
7
Koldehoff M, Steckel NK, Beelen DW, Elmaagacli AH. Therapeutic application of small interfering RNA directed against bcr-abl transcripts to a patient with imatinib-resistant chronic myeloid leukaemia. Clin. Exp. Med. 7, 47–55 (2007). Davis ME, Zuckerman JE, Choi CH et al. Evidence of RNAi in humans from systemically administered siRNA via targeted
future science group
nanoparticles. Nature 464, 1067–1070 (2010). 8
Zuckerman JE, Gritli I, Tolcher A et al. Correlating animal and human Phase Ia/Ib clinical data with CALAA-01, a targeted, polymer-based nanoparticle containing siRNA. Proc. Natl Acad. Sci. USA 111, 11449–11454 (2014).
9
Editorial
Tabernero J, Shapiro GI, LoRusso PM et al. First-in-humans trial of an RNA interference therapeutic targeting VEGF and KSP in cancer patients with liver involvement. Cancer Discov. 3, 406–417 (2013).
10 Nishimura M, Jung EJ, Shah MY et al.
Therapeutic synergy between microRNA and siRNA in ovarian cancer treatment. Cancer Discov. 3m 1302–1315 (2013).
www.futuremedicine.com
187
