FDA Approves Clinical Protocol for Additional Phase 1 Study of TKM-PLK1 in Primary Liver Cancer or Liver Metastases

The U.S. Food and Drug Administration approves the clinical protocol for an additional Phase 1 study of TKM-PLK1 in patients with either primary liver cancer or liver metastases associated with select cancers including ovarian.

RNA Interference

Nucleic acids are molecules that carry genetic information and include DNA (deoxyribonucleic acid) and RNA (ribonucleic acid). Together these molecules form the building blocks of life. DNA contains the genetic code or “blueprint” used in the development and functioning of all living organisms, while one type of RNA (i.e., “messenger RNA” or mRNA) helps to translate that genetic code into proteins by acting as a messenger between the DNA instructions located in the cell nucleus and the protein synthesis which takes place in the cell cytoplasm (i.e., outside the cell nucleus, but inside the outer cell membrane). Accordingly, DNA is first copied or transcribed into mRNA, which, in turn, gets translated or synthesized into protein.

The molecular origin of many diseases results from either the absence or over-production of specific proteins. “RNA interference” (RNAi) is a mechanism through which gene expression is inhibited at the translation stage, thereby disrupting the protein production. RNAi is considered one of the most important discoveries in the field of molecular biology. Andrew Fire, Ph.D., and Craig C. Mello, Ph.D. shared the 2006 Nobel Prize in Physiology or Medicine for work that led to the discovery of the RNAi mechanism.  Because many diseases – cancer, metabolic, infectious and others – are caused by the inappropriate activity of specific genes, the ability to silence genes selectively through RNAi offers the potential to revolutionize the way we treat disease and illness by creating a new class of drugs aimed at eliminating specific gene-products or proteins from the cell. RNAi has been convincingly demonstrated in preclinical models of oncology, influenza, hepatitis, high cholesterol, diabetes, macular degeneration, Parkinson’s disease, and Huntington’s disease.

Small Interfering RNA 

While the mechanism itself is termed “RNAi,” the therapeutic agents that exert the effect are known as “small interfering RNAs” or siRNAs. Sequencing of the human genome has provided the information needed to design siRNA therapeutics directed against a wide range of disease-causing proteins. Based on the mRNA sequence for the target protein, a siRNA therapeutic can be designed relatively quickly compared to the time needed to synthesize and screen conventional small molecule drugs. Moreover, siRNA-based therapeutics are able to bind to a target protein mRNA with great specificity. When siRNA are introduced into the cell cytoplasm they are rapidly incorporated into an “RNA-induced silencing complex” (RISC) and guided to the target protein mRNA, which is then cut and destroyed, preventing the subsequent production of the target protein. The RISC can remain stable inside the cell for weeks, destroying many more copies of the target mRNA and maintaining target protein suppression for long periods of time.

To our knowledge, there are no siRNAs approved yet for medical use outside of a clinical trial, however, a number of R&D initiatives and clinical trials are currently underway, with one of the main areas of research focused on delivery. Because siRNAs are large, unstable molecules, they are unable to access target cells. Delivery technology is required to stabilize these drugs in the human blood stream, allow efficient delivery to the target cells, and facilitate uptake and release into the cell cytoplasm. Tekmira Pharmaceuticals Corporation, a leading developer of RNAi therapeutics has focused its research on identifying lipid nanoparticles (LNPs) that can overcome the challenges of delivering siRNAs.

TKM-PLK1 

TKM-PLK1 is being developed as a novel anti-tumor drug in the treatment of cancer. LNPs are particularly well suited for the delivery of siRNA to treat cancer because the lipid nanoparticles preferentially accumulate within tissues and organs having leaky blood vessels, such as cancerous tumors. Once at the target site, LNPs are taken up by tumor cells and the siRNA payload is delivered inside the cell where it reduces expression of the target protein. Through careful selection of the appropriate molecular targets, LNPs are designed to have potent anti-tumor activity yet be well tolerated by healthy tissue adjacent to the tumor.

Tekmira has taken advantage of this passive targeting effect to develop an siRNA directed against PLK1 (polo-like kinase 1), a protein involved in tumor cell proliferation. Inhibition of PLK1 prevents the tumor cell from completing cell division, resulting in cell cycle arrest and cell death.

Because the standard of care for cancer treatment often involves the use of drug combination therapies, Tekmira has selected gene targets for its oncology applications that synergize with conventional drugs that are currently in use. TKM-PLK1 has the potential to provide both direct tumor cell killing and sensitization of tumor cells to the effects of chemotherapy drugs.

Phase 1 Study of TKM-PLK1 in Primary Liver Cancer or Liver Metastases

Tekmira, along with its collaborators at the U.S. National Cancer Institute (NCI), announced that they have received approval from the U.S. Food and Drug Administration (FDA) to proceed with a new Phase 1 clinical trial for Tekmira’s lead oncology product, TKM-PLK1. This trial, run in parallel with the ongoing Phase 1 trial of TKM-PLK1 (for adult patients with solid tumors or lymphomas that are refractory to standard therapy), provides Tekmira with an early opportunity to validate the mechanism of drug action.

“Patients in this new study, who will have either primary liver cancer or liver metastases, will receive TKM-PLK1 delivered directly into the liver via Hepatic Artery Infusion (HAI). The trial design will allow us to measure tumor delivery, polo-like kinase 1 (PLK1) messenger RNA knockdown, and RNA interference (RNAi) activity in tumor biopsies from all of the patients treated,” said Dr. Mark J. Murray, Tekmira’s President and CEO.

“This NCI clinical trial will run in parallel with our multi-center TKM-PLK1 solid tumor Phase 1 trial, currently underway at three centers in the United States. Working together on this clinical trial with our collaborators at the NCI will allow us to develop an even more robust data package to inform subsequent TKM-PLK1 development. We expect to have interim TKM-PLK1 clinical data before the end of 2011,” added Dr. Murray.

The NCI trial is a Phase 1 multiple-dose, dose escalation study testing TKM-PLK1 in patients with unresectable colorectal, pancreatic, gastric, breast, ovarian and esophageal cancers with liver metastases, or primary liver cancers. These patients represent a significant unmet medical need as they are not well served by currently approved treatments.

The primary objectives of the trial include evaluation of the feasibility of administering TKM-PLK1 via HAI, and characterization of the pharmacokinetics and pharmacodynamics of TKM-PLK1. Pharmacodynamic measurements will examine the effect of the drug on the patient’s tumors, specifically aiming to confirm PLK1 knockdown and RNAi activity. Typically reserved for later stage trials, pharmacodynamic measurements are facilitated in this Phase 1 trial in part through the unique capabilities of the NCI Surgery Branch. Secondary objectives of the trial include establishing maximum tolerated dose and to evaluate response rate.

About the National Cancer Institute

The National Cancer Institute (NCI) is one of 27 institutes and centers under the oversight of the U.S. National Institutes of Health (NIH), and is the primary cancer medical research agency in the U.S. The TKM-PLK1 trial will involve investigators at the NCI’s Center for Cancer Research (CCR) on the main NIH campus located in Bethesda, Maryland. The CCR is home to more than 250 scientists and clinicians working in intramural research at the NCI. CCR’s investigators include some of the worlds most experienced basic, clinical, and translational scientists who work together to advance our knowledge of cancer and develop new therapies.

About TKM-PLK1

TKM-PLK1 targets polo-like kinase 1, or PLK1, a cell cycle protein involved in tumor cell proliferation and a validated oncology target. Cancer patients whose tumors express high levels of PLK1 have a relatively poor prognosis. Inhibition of PLK1 prevents tumor cells from completing cell division, resulting in cell cycle arrest and cancer cell death.

About RNAi and Tekmira’s LNP Technology

RNAi therapeutics have the potential to treat a broad number of human diseases by “silencing” disease causing genes. The discoverers of RNAi, a gene silencing mechanism used by all cells, were awarded the 2006 Nobel Prize for Physiology or Medicine. RNAi therapeutics, such as “siRNAs,” require delivery technology to be effective systemically. LNP technology is one of the most widely used siRNA delivery approaches for systemic administration. Tekmira’s LNP technology (formerly referred to as “stable nucleic acid-lipid particles” or SNALP) encapsulates siRNAs with high efficiency in uniform lipid nanoparticles which are effective in delivering RNAi therapeutics to disease sites in numerous preclinical models. Tekmira’s LNP formulations are manufactured by a proprietary method which is robust, scalable and highly reproducible and LNP-based products have been reviewed by multiple FDA divisions for use in clinical trials. LNP formulations comprise several lipid components that can be adjusted to suit the specific application.

About Tekmira Pharmaceuticals Corporation

Tekmira Pharmaceuticals Corporation is a biopharmaceutical company focused on advancing novel RNAi therapeutics and providing its leading lipid nanoparticle delivery technology to pharmaceutical partners. Tekmira has been working in the field of nucleic acid delivery for over a decade and has broad intellectual property covering LNPs. Further information about Tekmira can be found at www.tekmirapharm.com. Tekmira is based in Vancouver, British Columbia, Canada.

Source

Clinical Trial Information

  • A Phase 1 Dose Escalation Study to Determine the Safety, Pharmacokinetics, and Pharmacodynamics of Intravenous TKM-080301 [a/k/a TKM-PLK1 or PLK1 SNALP] in Patients With Advanced Solid Tumors [or Lymphomas], ClinicalTrials.gov Identifier: NCT01262235. [Note: This clinical trial summary relates to the ongoing Phase 1 TKM-PLK1  solid tumor clinical trial. We will post the second Phase 1 TKM-PLK1 clinical trial summary with respect to primary liver cancer and liver metastases once it becomes publicly available]
Additional Information
  • Wang J, et al. Delivery of siRNA therapeutics: barriers and carriers. AAPS J. 2010 Dec;12(4):492-503. Epub 2010 Jun 11. Review. PubMed PMID: 20544328; PubMed Central PMCID: PMC2977003.

ASCO 2011: Novel Multi-targeted Agent Cabozantinib (XL184) Has Significant Effect on Several Advanced Solid Tumors

Cabozantinib (XL184) demonstrated high rates of disease control in patients with prostate, ovarian and liver cancers. The investigators concluded that cabozantinib exhibits clinical activity in ovarian cancer patients with advanced disease, regardless of prior platinum drug status, as reflected by the high rates of response. 

ASCO Releases Studies From Upcoming Annual Meeting – Important Advances in Targeted Therapies, Screening, and Personalized Medicine

The American Society of Clinical Oncology (ASCO) today highlighted several studies in a press briefing from among more than 4,000 abstracts publicly posted online at http://www.asco.org in advance of ASCO’s 47th Annual Meeting. An additional 17 plenary, late-breaking and other major studies will be released in on-site press conferences at the Annual Meeting.

The meeting, which is expected to draw approximately 30,000 cancer specialists, will be held June 3-7, 2011, at McCormick Place in Chicago, Illinois. The theme of this year’s meeting is “Patients. Pathways. Progress.”

“This year marks the 40th anniversary of the signing of the National Cancer Act, a law that led to major new investments in cancer research. Every day in our offices, and every year at the ASCO meeting, we see the results of those investments. People with cancer are living longer, with a better quality of life, than ever before,” said George W. Sledge Jr., M.D., President of ASCO, Ballve-Lantero Professor of Oncology and professor of pathology and laboratory medicine at the Indiana University School of Medicine.

“With our growing understanding of the nature of cancer development and behavior, cancer is becoming a chronic disease that a growing number of patients can live with for many years,” said Dr. Sledge. “The studies released today are the latest examples of progress against the disease, from new personalized treatments, to new approaches to screening and prevention.”

The study results from a phase II clinical trial involving cabozantinib (XL184) were highlighted today in the ASCO press briefing, as summarized below.

Novel Multi-targeted Agent Cabozantinib (XL184) Has Significant Effect on Several Advanced Solid Tumors, and Can Shrink or Eliminate Bone Metastases 

Cabozantinib (XL184) – an oral inhibitor of MET and VEGFR2 kinases involved in the development and progression of many cancers – showed strong responses in patients with various advanced cancers in a phase II trial. The drug demonstrated particularly high rates of disease control for advanced prostate, ovarian and liver cancers, which are historically resistant to available therapies. The drug also fully or partially eliminated bone metastases in patients with breast and prostate cancers and melanoma.

Michael S. Gordon, M.D., President & Chief Executive Officer, Pinnacle Oncology Hematology.

“Cabozantinib appears to have significant effects on several treatment-resistant tumors, as well as impressive effects on bone metastases. In addition, these effects are associated with rapid improvement in pain, a reduction in opiate narcotic requirements and improvement in anemia,” said lead author Michael S. Gordon, M.D., a medical oncologist at Pinnacle Oncology Hematology located in Scottsdale, Arizona. “The implications of these results are very exciting—it is unusual to find a targeted therapy, absent of a molecular mutation in tumors, that works in bony disease and has this activity.”

To be eligible for the study, patients had to have advanced, progressive solid tumors, with or without bone metastases. Of 398 evaluable patients (of 483 enrolled in the trial), 39 percent had bone metastases at baseline. Patients received cabozantinib over 12 weeks. The trial was designed as a “discontinuation” trial, in which those who had partial responses stayed on the drug; those with stable disease were randomized to cabozantinib or placebo; and patients with progressive disease were removed from the trial. This novel type of clinical trial design more quickly evaluates the disease-stabilizing activity of growth-inhibitory agents like cabozantinib, compared to the traditional model of randomizing all patients to either the experimental arm or placebo.

Among 398 patients evaluable with all types of cancer included in the trial, the collective overall response rate was 9 percent (34 of 398). The highest disease control rates (partial response and stable disease) at week 12 were 76 percent for liver cancer (22 of 29 patients), 71 percent for prostate cancer (71 of 100 patients), and 58 percent for ovarian cancer (32 of 51 patients). [emphasis added].

Of the 51 evaluable ovarian cancer patients noted above, 28 are platinum drug resistant, 17 are platinum drug sensitive, and 6 have unknown status. The median number of systemic treatments prior to trial enrollment was 2. The overall response rate (complete response and partial response based on modified RECIST criteria) for ovarian cancer was 12/51 (24%).  Upon breakdown, the response rate was 5/28 (18%) for platinum drug resistant patients, and 5/17 (29%) for platinum drug sensitive patients. Five additional partial responses await confirmation. After a median follow-up of 4 months (range: 1 to 11 months), the median duration of response and median progression free survival have not been reached. The most common related adverse events ( ≥grade 3) among ovarian cancer patients were hand-foot syndrome (10%), diarrhea (8%) and fatigue (4%). Drug dose reductions and permanent discontinuations for adverse events occurred in 43% and 10% of the ovarian cancer patients, respectively. Based on these findings, the investigators concluded that cabozantinib exhibits clinical activity in ovarian cancer patients with advanced disease, regardless of prior platinum drug status, as reflected by the high rates of response. [emphasis added] Accordingly, randomization in the ovarian cancer cohort was halted & patients unblinded due to the observed high efficacy.

Fifty-nine of 68 patients with bone metastases (including patients with breast and prostate cancers and melanoma) experienced either partial or complete disappearance of the cancer on bone scans, often with significant pain relief and other improved cancer-related symptoms.

The reduction of bone metastases and pain relief was an unexpected finding in this study, Dr. Gordon said. Independent review by radiologists confirmed that bone metastases disappeared in the majority of patients who had bone metastases when they entered the study. The majority of these patients had castration-resistant prostate cancer (CRPC), but patients with breast cancer and melanoma also had disappearance of bone metastases. Bone metastases greatly contribute to morbidity and mortality in patients with these types of cancer, which typically spread to the bone.

Due to these results, the study has been expanded to include more CRPC patients. Similarly, the high rate of lasting responses in ovarian cancer patients led researchers to also expand the study to evaluate the drug’s effect on patients with a particularly resistant form of the disease known as platinum drug resistant/refractory ovarian cancer. [emphasis added]

This study expansion results will help determine the design of future phase III trials, which will assess whether the drug extends patients lives or has other longer-term benefits among patients with specific cancer types. At present, cabozantinib is being investigated for use as a single agent. Additional studies will evaluate the efficacy and tolerability of appropriate combinations with other agents for future indications.

For the solid tumor patients collectively, the most common grade three or above adverse events were fatigue (9 percent) and hand-foot syndrome (8 percent). Dose reductions were required in 41 percent of patients due to side effects; 12 percent were removed from the trial for adverse events.

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Outside-the-Box: The Rogosin Institute Is Fighting Cancer With Cancer Cells In Clinical Trials

Researchers at the Rogosin Institute are using cancer “macrobeads” to fight cancer.  Cancer cells in the beads secrete proteins which researchers believe could signal a patient’s cancer to stop growing, shrink or even die. The treatment is currently being tested in human clinical trials.

Two groundbreaking preclinical studies demonstrate for the first time that encapsulated mouse kidney cancer cells inhibit the growth of freely-growing cancer cells of the same or different type in a laboratory dish and in tumor-bearing animals. These findings support the hypothesis that cancer cells entrapped in seaweed-based gel, called “macrobeads,” send biological feedback or signals to freely-growing tumors outside the macrobead to slow or stop their growth. Both studies (cited below) are published in the on-line January 24, 2011 issue of Cancer Research, a publication of the American Association For Cancer Research.

Barry H. Smith, M.D., Ph.D., Director, The Rogosin Institute; Professor, Clinical Surgery, Weill Cornell Medical College

The Rogosin Institute, an independent not-for-profit treatment and research center associated with New York-Presbyterian Hospital and Weill Cornell Medical College, developed the cell encapsulation technology that facilitated production of the macrobead and applied this technology in conducting preclinical studies. The research team was headed by Barry H. Smith, M.D., Ph.D.,  the Director of The Rogosin Institute, Professor of Clinical Surgery at the Weill Cornell Medical College, and lead author of the studies. Findings in the studies to date are consistent with the hypothesis that when macrobeads are implanted in a host, the encapsulated cells are isolated from the host’s immune system but continue to maintain their functionality.

In addition to the standard preclinical in vivo and in vitro experiments, a clinical veterinary study was conducted in cats and dogs suffering from various spontaneous (non-induced) cancers. More than 40 animals were treated with the macrobead technology. Consistent results, measured both in terms of tumor response and animal well-being, occurred with prostate, liver and breast cancer, as well as lymphoma. Additional research revealed that regardless of the animal specie or type of cancer cell that was encapsulated, the macrobead technology inhibited cancer growth across all species and cancer types tested.  The results have included slowed tumor growth or, in some cases, necrosis and elimination of tumors and the restoration of a normal animal lifespan.

Cancer macrobead therapy has proceeded to human clinical testing. A Phase 1 trial in more than 30 patients evaluated the safety of macrobeads implanted in the abdominal cavity as a biological treatment of end-stage, treatment-resistant, epithelial-derived cancer. Based on the safety profile data, Phase 2 efficacy trials are in progress in patients with colorectal cancer, pancreatic cancer and prostate cancer. The Phase 1 trial remains open to a range of epithelial-derived cancers, including ovarian.  To date, the Rogosin Institute research team has not found evidence to indicate that placing mouse tumors in humans or other animal species causes harm or side-effects.

Scientists are testing whether macrobeads containing cancer cells can be implanted into patients and communicate with the patient’s tumor to stop growing, shrink or die.

Step 1:  Small beads are made from a seaweed-derived sugar called agarose and mixed with 150,000 mouse kidney cancer cells, and a second layer of agarose is added, encapsulating the cancer cells.

Step 2:  Within 3-to-10 days, 99% of the kidney cancer cells die.  The remaining cells have traits similar to cancer stem cells.

Step 3:  The stem cells begin to recolonize the bead.  The colonies increase in sufficient numbers within a few weeks to reach a stable state.

Step 4:  The beads begin to release proteins —  chemical signals reflecting that the beads have sufficient numbers of cells for growth regulators to kick in.

Step 5: Several hundred beads (depending on patient’s weight) are implanted in the abdominal cavity in a laparoscopic surgical procedure.  The cancer cells are trapped in the beads; preventing their circulation elsewhere in the body and protecting them from attack by the body’s immune system.

Step 6: In animal studies, researchers believe some proteins released from the beads reached tumors elsewhere in the body and tricked them into sensing that other tumor cells are nearby.

Step 7:  As a result, researchers believe tumors in some animals stopped growing, shrank or died.  The hypothesis is being tested in people with cancer.

Howard Parnes, M.D., Chief, Prostate & Urologic Cancer Research Group, Division of Cancer Prevention, National Cancer Institute

“This is a completely novel way of thinking about cancer biology,” says Howard L. Parnes, a researcher in the Division of  Cancer Prevention at the National Cancer Institute who is familiar with the work but was not involved with it. “We talk about thinking outside the box. It’s hard to think of a better example.” “They demonstrate a remarkable proof of principle that tumor cells from one animal can be manipulated to produce factors that can inhibit the growth of cancers in other animals,” Dr. Parnes says. “This suggests that these cancer inhibitory factors have been conserved over millions of years of evolution.”

“Macrobead therapy holds promise as a new option in cancer treatment because it makes use of normal biological mechanisms and avoids the toxicities associated with traditional chemotherapy,” said Dr. Barry Smith. “The results of our research show that this approach is not specific to tumor type or species so that, for example, mouse cells can be used to treat several different human tumors and human cells can be used to treat several different animal tumors.”

“Because cancer and other diseases are their own biological systems, we believe that the future of effective disease treatment must likewise be biological and system-based,” said Stuart Subotnick, CEO of Metromedia Bio-Science LLC. “Many of the existing therapies are narrow, targeted approaches that fail to treat diseases comprehensively. In contrast, our unique macrobead technology delivers an integrated cell system that alters disease processes and utilizes the body’s natural defense mechanisms. The goal is to repair the body and not merely treat the symptoms.”

It is well-known that proof of anti-tumor activity in treating animals does not represent guaranteed effectiveness in humans. But, assuming the macrobead therapy proves ultimately effective in humans, it would represent a novel approach to treating cancer and challenge existing scientific dogmas.

The cancer macrobead therapy described above is backed by Metromedia Company, a privately held telecommunications company which was run by billionaire John Kluge until his recent death. The Metromedia Biosciences unit has invested $50 million into the research.  If the treatment proves successful in humans, a large part of the revenue generated will be contributed to Mr. Kluge’s charitable foundation.

About Metromedia Bio-Science LLC

Metromedia Bio-Science LLC, in conjunction with The Rogosin Institute, utilizes the novel cell encapsulation technology to conduct research into the treatment of various diseases, including cancer and diabetes, and the evaluation of disease therapies. Metromedia Bio-Science LLC is an affiliate of Metromedia Company, a diversified partnership founded by the late John W. Kluge and Stuart Subotnick.

About The Rogosin Institute

The Rogosin Institute is an independent not-for-profit treatment and research center associated with New York-Presbyterian Hospital (NYPH) and Weill Cornell Medical College. It is one of the nation’s leading research and treatment centers for kidney disease, providing services from early stage disease to those requiring dialysis and transplantation. It also has programs in diabetes, hypertension and lipid disorders. The Institute’s cancer research program, featuring the macrobeads, began in 1995. The Rogosin Institute is unique in its combination of the best in clinical care with research into new and better ways to prevent and treat disease.

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