Canadian Adverse Reaction Newsletter, Volume 24 - Issue 1 - January 2014

ISSN 1499-9447
Cat no H42-4/1-24-1E

Health Products and Food Branch
Marketed Health Products Directorate
Canadian Adverse Reaction Newsletter Editorial Team

In this Issue:

• Vascular endothelial growth factor receptor inhibitors and thrombotic microangiopathy
• Incidents involving the combined use of Durepair Dura Regeneration Matrix with ancillary wound closure products
• Summary of advisories

Scope

This quarterly publication alerts health professionals to potential signals detected through the review of case reports submitted to Health Canada. It is a useful mechanism to stimulate adverse reaction reporting as well as to disseminate information on suspected adverse reactions to health products occurring in humans before comprehensive risk-benefit evaluations and regulatory decisions are undertaken. The continuous evaluation of health product safety profiles depends on the quality of your reports.

Reporting Adverse Reactions
Canada Vigilance Program
Phone: 1-866-234-2345
Fax: 1-866-678-6789

For more information on how to report an adverse reaction, visit the Reporting Adverse Reactions to Drugs and Other Health Products page.

Caveat:  Adverse reactions (ARs) to health products are considered to be suspicions, as a definite causal association often cannot be determined. Spontaneous reports of ARs cannot be used to estimate the incidence of ARs because ARs remain underreported and patient exposure is unknown.

Vascular endothelial growth factor receptor inhibitors and thrombotic microangiopathy

Vascular endothelial growth factor (VEGF) and its receptors play a central role in tumour angiogenesis.^{Reference 1}  Blockade of this pathway is considered to be a therapeutic strategy to inhibit tumour growth. Anti-VEGF agents block the VEGF pathway by generally one of 2 mechanisms - by preventing the interaction of VEGF with its receptor (i.e., VEGF antagonists, which include anti-VEGF monoclonal antibodies such as bevacizumab) or by targeting surface receptor function (i.e., VEGF receptor inhibitors, the focus of this article).

Six marketed VEGF receptor inhibitors are available in Canada (Table 1). The risk of thrombotic microangiopathy (TMA) is currently labelled in the Post-Marketing Experience section of the sunitinib (Sutent) Canadian product monograph (CPM) and in the Warnings and Precautions, Adverse Reactions and Post-Market Adverse Drug Reactions sections of the pazopanib (Votrient) CPM.^{Reference 2},^{Reference 3}

TMAs are a group of disorders characterized by occlusive microvascular thrombosis, thrombocytopenia and end-organ damage.^{Reference 4} Two main subtypes of TMA are thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS). Clinical symptoms of TTP typically include thrombocytopenia, microangiopathic hemolytic anemia (MAHA), neurological abnormalities, renal failure and fever. HUS can present with similar signs and symptoms, however HUS is usually diagnosed in cases in which renal failure is the most prominent sign. A diagnosis of TTP is generally designated for cases in which neurologic abnormalities such as seizure and vision loss predominate.

Several cases of TMA involving sunitinib have been published in the literature.^{Reference 5},^{Reference 6},^{Reference 7},^{Reference 8},^{Reference 9},^{Reference 10} In some of these cases, clinical manifestations of TMA resolved or improved upon discontinuation of sunitinib (along with management therapy).^{Reference 5},^{Reference 6},^{Reference 8},^{Reference 10}  In one case, renal function remained normal, and laboratory investigations did not indicate any signs of TMA, however a renal biopsy later revealed features typical of TMA.^{Reference 7}  This case highlights the possible discrepancy between mild clinical manifestations and severe TMA features on renal biopsy. Although most cases of anti-VEGF agent-induced TMA appear to be localized to the kidneys, systemic organ dysfunction can occur.^{Reference 11} For example, 5 cases of systemic TMA involving MAHA were reported in patients receiving a combination of sunitinib and bevacizumab.^{Reference 12}

While VEGF receptor inhibitors are suspected of being associated with TMA, the exact mechanism of this association is unclear. A compromised renal endothelium is the proposed mechanism underlying TMA-related adverse reactions.^{Reference 13} This association does not exclude the possibility of other contributing factors or pathways.^{Reference 7},^{Reference 8}  Although not the focus of the current article, published cases of TMA or suspected TMA have also been reported with VEGF antagonists.^{Reference 13},^{Reference 14} Considering that TMA has been observed with the use of multiple anti-VEGF agents, it has been suggested that this risk may represent a class effect.^{Reference 4},^{Reference 7}

As of June 30, 2013, Health Canada has not received any reports of TMA such as TTP or HUS suspected of being associated with any of the 6 VEGF receptor inhibitors marketed in Canada.

Health care professionals are reminded that this adverse reaction may be underdiagnosed and underreported. Management of TMA should focus on strict monitoring and early recognition of signs and symptoms in patients treated with anti-VEGF agents.^{Reference 4} Health care professionals are encouraged to report to Health Canada any cases of TMA such as TTP or HUS suspected of being associated with anti-VEGF agents.

Rania Mouchantaf, PhD, Health Canada

Incidents involving the combined use of Durepair Dura Regeneration Matrix with ancillary wound closure products

Durepair Dura Regeneration Matrix is a collagen implant used to repair dura mater defects during neurosurgery. It is a dural graft substitute derived from fetal bovine dermis.^{Reference 1} During implantation, Durepair may either be sutured into place or applied as an onlay graft.^{Reference 2} The porous structure of Durepair allows for fibroblast infiltration and vascularization of the implant, and eventual remodelling of the site with native collagen^{Reference 1}.

As of October 15, 2013, Health Canada received 5 reports of medical device incidents suspected of involving Durepair. In one incident, it was reported that a Durepair graft implanted in a patient in conjunction with Tisseel fibrin sealant was later removed and had a texture similar to toothpaste. The other 4 cases described patients developing chemical (or aseptic) meningitis after implantation with Durepair. In one of these 4 cases, the Durepair was implanted in conjunction with Tisseel fibrin sealant and revision surgery was required. In the other 3 of these 4 cases, it was unknown whether ancillary wound closure products (e.g., sealants, hemostatics) were used in conjunction with Durepair. The Tisseel product monograph states that its safety and effectiveness in neurosurgical procedures has not been evaluated.^{Reference 3}

Known complications associated with the use of dural grafts are often hydrodynamic in nature, and include cerebrospinal fluid (CSF) leakage, pseudomeningocele, chemical (or aseptic) meningitis, and delayed hydrocephalus.^{Reference 4}  However, nonrandomized studies have shown results suggesting a possible increased risk of complications when ancillary wound closure products are used in combination with collagen duraplasty grafts,^{Reference 5},^{Reference 6} including Durepair.^{Reference 7} One study found that 5 out of 9 patients receiving Durepair in combination with DuraSeal dural sealant (a polyethylene glycol hydrogel) experienced hydrodynamic complications and that 3 out of 9 patients required reoperation. All 5 complications presented 16 days after surgery or later and the authors suggested that the use of ancillary sealant may have inhibited cell migration in the area of the graft, hence delaying postsurgical inflammation and healing.^{Reference 7}

Other researchers have also postulated that the use of ancillary sealants may reduce the efficacy of a collagen dural graft over time, possibly by impairing conductivity, leading to graft decay without native tissue repair.^{Reference 6}  However, increases in complications may be related to the tendency to use multiple products in cases with higher perceived risk of CSF leak (or other hydrodynamic complications) at the outset.^{Reference 6} There are no published randomized clinical trials specifically investigating this issue. However, the Durepair Instructions for Use state "Animal study results suggest that the foreign body response associated with the use of sealants and hemostatic agents in conjunction with Durepair may be more pronounced than use of Durepair alone. This response may increase the incident rates of known risks of dura substitutes".^{Reference 2} Physicians are encouraged to consult the product labelling of ancillary products when considering their concomitant use with Durepair.

Andrew Gaffen, DDS, MSc, Health Canada

Looking for old issues of CARN?

CARN issues from January 2000 to present are available in the Index of Published Canadian Adverse Reaction Newsletters on the Health Canada Web site.

• Those published prior to April 2011 have been marked as archived as part of the Government of Canada Web Standards initiative.
• What does this mean? When accessing the file in PDF format, the CARN is reproduced in its entirety; however archived issues now begin on the second page. The publication itself has not been altered or updated.

CARN issues from October 1996 to present are also available online in the  Electronic Collection of Library and Archives Canada in original format.

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Canadian Adverse Reaction Newsletter

Health Canada
Marketed Health Products Directorate
Address Locator 0701D
Ottawa ON K1A 0K9
Telephone: 613-954-6522
Fax: 613-952-7738

Editorial Team
Patricia Carruthers-Czyzewski, BScPhm, MSc (Editor-in-Chief)
Christianne Scott, BPharm, MBA
Jared Cousins, BSP
Hoa Ly, BSc
Emir Al-Khalili, RPh, BScPhm, MSc
Nicoleta Hosszu Ungureanu, Msc

Acknowledgement
We thank the following members of the Expert Advisory Committee on the Vigilance of Health Products for their review of material for this issue: Colleen J. Metge, BSc(Pharm), PhD; Yola Moride, PhD, FISPE; Rishma Walji, ND, PhD; and Darrel Forsythe, RN, BN, ACCN. We also thank Sally Pepper, RPh, BScPhm; Sylvie Martin, MD; and Mélanie Bousquet, PhD, as well as Alexandre Pratt; Kristina Klinovski, BSc; and Rachel Mailhot, students in Biomedical Sciences, Occupational Therapy and Biomedical Sciences, respectively, for their participation in the production of the newsletter.

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Reporting Adverse Reactions
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Fax: 1-866-678-6789

Copyright
© 2014 Her Majesty the Queen in Right of Canada. This publication may be reproduced without permission provided the source is fully acknowledged. The use of this publication for advertising purposes is prohibited. Health Canada does not assume liability for the accuracy or authenticity of the information submitted in case reports.

Due to time constraints relating to the production of this publication, information published may not reflect the most current information.