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The "regulatory paradox" is a tension between aversion to uncertainty and willingness to accept unknowns about a drug before its approval. Finding the right balance may mean the difference between fostering and stifling innovation. Clinical pharmacology applied in the drug development and regulatory contexts can bridge mechanistic reasoning and empiricism to help reconcile the regulatory paradox. Here, we propose that the discipline of clinical pharmacology, in the regulatory setting, is well positioned to build on its past successes in the advancement and acceleration of drug development.

The FDA is developing guidance on the use of “real-world evidence” — health care information from atypical sources, including electronic health records, billing databases, and product and disease registries — to assess the safety and effectiveness of drugs and devices.

The continued development of new antibacterial drugs is critical to meet patient and public health needs. In this editorial, authors from the US Food and Drug Administration and European Medicines Agency reflect on the role of public-private partnerships and the development of clinical trials networks as agents to guide and perform quality studies of antibacterial drugs.

The FDA has committed to working with other agencies, health care providers, industry, and patients and families to deal proactively with the opioid abuse crisis, while safeguarding appropriate access to vitally important pain medications for the patients who need them.

To improve access to biologic drugs, Congress authorized the FDA to create an abbreviated pathway for approving biologics that are “biosimilar” to approved products. Reconciling the science of biosimilar development with a new regulatory framework is challenging.

Contemporary medicine is a large and complex system involving many participants, all of whom play a critical role in managing the risks intrinsic to medical product use. Despite the robust premarket review and approval process of the U.S. Food and Drug Administration (FDA), new information will inevitably be learned in the postmarketing period about the safety of medicines and how they are and should be used. For much of this information, FDA relies on public reports about possible adverse events. In turn, the public depends on FDA to communicate the most up-to-date safety information on medical products to better inform treatment decisions. Expanding the scope and strengthening the capabilities of the drug safety surveillance system are among key FDA projects designed to reduce avoidable injury and death from medication use. Although improving drug safety is our goal and obligation to the public, FDA cannot protect the public adequately without the active involvement of all participants in healthcare.

There is an ongoing debate over the evidentiary standards that should be applied for introduction of new diagnostics into routine clinical practice. Many call for evidence of "clinical utility," i.e., a positive impact on patient outcomes. A diagnostic, when used with a medicine, has clinical utility if it improves the outcomes of drug therapy. Improved outcomes may be defined broadly, including benefits, harm reduction, and patient-reported outcomes. Much of the controversy centers around the methods of demonstrating clinical utility. For instance, are randomized prospective trials the only acceptable source of data? Practically speaking, many sources of evidence-mechanistic, pharmacologic, and observational-can contribute to a finding of clinical utility, depending on the circumstances. Clinical utility is highly indication specific, and achieving it is dependent on good analytical and diagnostic test performance.

Dr Janet Woodcock is the Director of the US FDA’s Center for Drug Evaluation and Research. Dr Woodcock has held various positions within the FDA’s Office of the Commissioner from October 2003 until 1 April 2008, as Deputy Commissioner and Chief Medical Officer, Deputy Commissioner for Operations and Chief Operating Officer and Director of the Critical Path Programs. She oversaw scientific and medical regulatory operations for the FDA. Dr Woodcock served as Director of the Center for Drug Evaluation and Research at the FDA from 1994 to 2005. She previously served in other positions at the FDA, including Director of the Office of Therapeutics Research and Review and Acting Deputy Director of the Center for Biologics Evaluation and Research. Dr Woodcock received her MD from Northwestern Medical School (IL, USA), and completed further training and held teaching appointments at the Pennsylvania State University (PA, USA) and the University of California in San Francisco (CA, USA). She joined the FDA in 1986. Bioanalysis spoke with Dr Janet Woodcock on 21 June 2010.

Gomes and colleagues explore the trends and consequences of the recent and striking increase in gabapentinoid prescribing, particularly in combination with opioids. The editorialists discuss these ...

This March 2009 Workshop Summary Report was sponsored by Product Quality Research Institute (PQRI) based on a proposal by the Inhalation and Nasal Technology Focus Group (INTFG) of the American Association of Pharmaceutical Scientists (AAPS). Participants from the pharmaceutical industry, academia and regulatory bodies from the United States, Europe, India, and Brazil attended the workshop with the objective of presenting, reviewing, and discussing recommendations for demonstrating bioequivalence (BE) that may be considered in the development of orally inhaled drug products and regulatory guidances for new drug applications (NDAs), abbreviated NDAs (ANDAs), and postapproval changes. The workshop addressed areas related to in vitro approaches to demonstrating BE, biomarker strategies, imaging techniques, in vivo approaches to establishing local delivery equivalence and device design similarity. The workshop presented material that provided a baseline for the current understanding of orally inhaled drug products (OIPs) and identified gaps in knowledge and consensus that, if answered, might allow the design of a robust, streamlined method for the BE assessment of locally acting inhalation drugs. These included the following: (1) cascade impactor (CI) studies are not a good 2 predictor of the pulmonary dose; more detailed studies on in vitro/in vivo correlations (e.g., suitability of CI studies for assessing differences in the regional deposition) are needed; (2) there is a lack of consensus on the appropriate statistical methods for assessing in vitro results; (3) fully validated and standardized imaging methods, while capable of providing information on pulmonary dose and regional deposition, might not be applicable to the BE of inhaled products mainly due to the problems of having access to radiolabeled innovator product; (4) if alternatives to current methods for establishing local delivery BE of OIPs cannot be established, biomarkers (pharmacodynamic or clinical endpoints) with a sufficiently steep dose-response need to be identified and validated for all relevant drug classes; and (5) the utility of pharmacokinetic studies for evaluating "local pulmonary delivery" equivalence deserves more attention. A summary of action items for seminars and working groups to address these topics in the future is also presented.

BACKGROUND There is an urgent need to determine whether oversulfated chondroitin sulfate (OSCS), a compound contaminating heparin supplies worldwide, is the cause of the severe anaphylactoid reactions that have occurred after intravenous heparin administration in the United States and Germany. METHODS Heparin procured from the Food and Drug Administration, consisting of suspect lots of heparin associated with the clinical events as well as control lots of heparin, were screened in a blinded fashion both for the presence of OSCS and for any biologic activity that could potentially link the contaminant to the observed clinical adverse events. In vitro assays for the activation of the contact system and the complement cascade were performed. In addition, the ability of OSCS to recapitulate key clinical manifestations in vivo was tested in swine. RESULTS The OSCS found in contaminated lots of unfractionated heparin, as well as a synthetically generated OSCS reference standard, directly activated the kinin-kallikrein pathway in human plasma, which can lead to the generation of bradykinin, a potent vasoactive mediator. In addition, OSCS induced generation of C3a and C5a, potent anaphylatoxins derived from complement proteins. Activation of these two pathways was unexpectedly linked and dependent on fluid-phase activation of factor XII. Screening of plasma samples from various species indicated that swine and humans are sensitive to the effects of OSCS in a similar manner. OSCS-containing heparin and synthetically derived OSCS induced hypotension associated with kallikrein activation when administered by intravenous infusion in swine. CONCLUSIONS Our results provide a scientific rationale for a potential biologic link between the presence of OSCS in suspect lots of heparin and the observed clinical adverse events. An assay to assess the amidolytic activity of kallikrein can supplement analytic tests to protect the heparin supply chain by screening for OSCS and other highly sulfated polysaccharide contaminants of heparin that can activate the contact system.

At FDA, bioinformatics means the design, development, and use of modem computer systems to efficiently and effectively manage the regulatory product information supply chain, along which medical product information travels among many relevant organizations. The FDA relies on efficient management of this information to assess a drug’s safety and effectiveness. The current bioinformatics infrastructure that supports product information exchange is inefficient and is comparable to the antiquated infrastructure of the financial industry inyears past. Bioinformatics modernization requires improvements in three important information management domains: access, standards, and interface. We must have better access to information, more standardized information, and better interface with information (ie, better tools to convert information into knowledge). The FDA has taken measurable steps to modernize its bioinformatics infrastructure, but the effort is costly, complex, and time consuming. Nonetheless, it is a necessary step to improve the Critical Path and enhance benefit-risk assessments of drugs.

Heparin has been used clinically as an anticoagulant for over 60 years. Typically isolated from porcine intestine, heparin is a mixture of dimeric glycosidic sequences generating complex polysaccharide glycosaminoglycan chains. Recently, certain lots of heparin have been associated with an acute, rapid onset of significant side effects indicative of an allergic-type reaction. To identify potential causes for this serious rise in side effects, we examined lots of heparin that correlated with adverse events using orthogonal high resolution analytical techniques. Through comparison of these results with those obtained on reference lots, suspect lots were found to contain a highly sulfated chondroitin sulfate contaminant. Through detailed structural analysis, the contaminant was found to contain a disaccharide repeat unit of glucuronic acid linked β1→3 to a β-galactosamine. Surprisingly, the disaccharide unit contains an unusual sulfation pattern and is sulfated at the 2-O and 3-O positions of the glucuronic acid as well as at the 4-O and 6-O positions of the galactosamine. The presence of such a contaminant could elicit a biological response as highly sulfated polysaccharides, such as dextran sulfate, are known to be potent mediators of the immune system. Given the nature of the contaminant, traditional screening tests - such as those present as part of the current United States Pharmacopeia heparin monograph - cannot differentiate between affected and unaffected lots. Our analysis suggests effective screening methods that can be employed to determine whether or not heparin lots contain the contaminants reported here.

Biomedical science has greatly improved our understanding of pain in recent decades, but few novel molecular entities that address fundamentally new pain mechanisms have entered the clinic, despite dramatically increased pharmaceutical investment. Indeed, virtually all new analgesics approved over the past 25 years are derivatives or reformulations of opioids or aspirin-like drugs, existing drugs given for a new indication or older drugs given by a different route of administration. Here, we discuss factors contributing to this lack of innovation in therapies for pain and advocate public-private partnerships (PPPs) to translate new knowledge into more efficacious and safer treatments.

The scientific and regulatory issues that are associated with the possible introduction of 'follow-on' versions of protein drug products are the topic of considerable debate at present. Because of the differences between protein drug products and small-molecule drugs, the development of follow-on versions of protein products presents more complex scientific challenges than those presented by the development of generic versions of small-molecule drugs. Here, with a view to illustrating the Food and Drug Administration's (FDA's) scientific reasoning and experience in this area, we discuss past examples of the FDA's actions involving the evaluation of various types of follow-on and second-generation protein products and within-product manufacturing changes. The FDA believes its evaluation of the safety and effectiveness of follow-on protein products will evolve as scientific and technological advances in product characterization and manufacturing continue to reduce some of the complexity and uncertainty that are inherent in the manufacturing of protein products.

The proceedings of a workshop focusing on a project to evaluate the use of fluorodeoxyglucose-positron emission tomography (FDG-PET) as a tool to measure treatment response in non-Hodgkin lymphoma (NHL) are described. Sponsored by the Leukemia & Lymphoma Society, the Foundation of the National Institutes of Health, and the National Cancer Institute, and attended by representatives of the Food and Drug Administration, the Centers for Medicare and Medicaid Services, and scientists and clinical researchers from academia and the pharmaceutical and medical imaging industries, the workshop reviewed the etiology and current standards of care for NHL and proposed the development of a clinical trial to validate FDG-PET imaging techniques as a predictive biomarker for cancer therapy response. As organized under the auspices of the Oncology Biomarker Qualification Initiative, the three federal health agencies and their private sector and nonprofit/advocacy group partners believe that FDG-PET not only demonstrates the potential to be used for the diagnosis and staging of many cancers but in particular can provide an early indication of therapeutic response that is well correlated with clinical outcomes for chemotherapy for this common form of lymphoma. The development of standardized criteria for FDG-PET imaging and establishment of procedures for transmission, storage, quality assurance, and analysis of PET images afforded by this demonstration project could streamline clinical trials of new treatments for more intractable forms of lymphoma and other cancers and, hence, accelerate new drug approvals.

There has been much recent discussion about the advent of "personalized medicine," but controversy exists over its exact definition; how, when, and whether it will be brought about, and what means could be used to measure its attainment. In fact, the concept of "personalized medicine" is a sort of shorthand used to represent the logical next steps in progression of medical science toward greater mechanistic understanding of health, disease, and treatment. This shorthand is attractive to the public because of its intuitive appeal, and irritating to the biomedical community because it glosses over the very real scientific and implementation challenges. This paper evaluates the trajectory and promise of these next steps for the currently problematic states of both drug development and therapy.

The October 2015 FDA/PQRI Conference on Advancing Product Quality provided a forum for the exchange of ideas focused on drug product quality between regulatory agencies, the pharmaceutical industry, and academia. Key topics of the 2015 conference were (i) emerging regulatory initiatives; (ii) regulatory submission, assessment, and inspection; (iii) product and process development; and (iv) manufacturing, risk management, and quality assurance. Key discussion points and recommendations for each track and session have been captured. With powerful advancements in product quality encompassing regulatory, industrial, and technological elements, an era of rapidly improving pharmaceutical quality is underway. At the conference, one theme prevailed through all sessions: regulators, industry, and academia are aligned in their desire for drug product quality on behalf of the ultimate stakeholder–the patient. 3D three dimensional, ANDA abbreviated new drug application, API active pharmaceutical ingredient, ASTM American society for testing and materials, BCS biopharmaceutics classification system, BLA biological license application, CGMP current good manufacturing practice, CMA critical material attribute, CMC chemistry manufacturing and controls, CPP critical process parameters, CQA critical quality attribute, CU content uniformity, DLS dynamic light scattering, DOE design of experiment, EMA European Medicines Agency, EWG Expert Working Group, FDA Food and Drug Administration, GDUFA generic drug user fee amendments, HCl Hydrogen Chloride, ICH International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use, IND investigational new drug, IQA integrated quality assessment, IR immediate release, IR information request, ISPE International Society for Pharmaceutical Engineering, MIT Massachusetts Institute of Technology, NDA new drug application, NIPP new inspection protocols project, NIR near-infrared spectroscopy, OPQ office of pharmaceutical quality, PAI pre-approval inspection, PAT process analytical technology, PDUFA prescription drug user fee act, PHS public health service, PQRI Product Quality Research Institute, PQS pharmaceutical quality system, QbD quality by design, QMS quality management system, QRM quality risk management, QTPP quality target product profile, RPM revolutions per minute, RTRT real time release testing, SUPAC scale-up and post-approval changes, UDU uniformity of dosage units, USP U.S. Pharmacopeial Convention.

Immunological and inflammatory processes downstream of dystrophin deficiency as well as metabolic abnormalities, defective autophagy, and loss of regenerative capacity all contribute to muscle pathology in Duchenne muscular dystrophy (DMD). These downstream cascades offer potential avenues for pharmacological intervention. Modulating the inflammatory response and inducing immunological tolerance to de novo dystrophin expression will be critical to the success of dystrophin-replacement therapies. This Review focuses on the role of the inflammatory response in DMD pathogenesis and opportunities for clinical intervention.

The four major epidermal keratins (65-67K, 58K, 56K, and 50K) have been localized in various cell layers of normal human epidermis. Guinea pig antisera and mouse monoclonal antibodies were prepared against human epidermal keratins and were characterized with respect to their specificity to individual keratin polypeptides by the immunoblot technique. These antibodies were used to stain vertical frozen sections of skin, and to identify keratins extracted from serial, horizontal skin sections. The results indicate that: (1) a 65-67K keratin component is limited to the suprabasal layers, (2) a 58K keratin is present throughout the epidermis, (3) a 56K keratin appears to be made only in cells above the basal layer, possibly in the upper spinous or granular layer, and (4) a 50K keratin is present in all living layers but is largely eliminated during stratum corneum formation. The 65-67K and 56K keratins, which are characteristic of suprabasal, terminally differentiated keratinocytes, may be regarded as molecular markers of keratinization.

The Food and Drug Administration (FDA) regulates pharmaceutical drug products to ensure a continuous supply of high-quality drugs in the USA. Continuous processing has a great deal of potential to address issues of agility, flexibility, cost, and robustness in the development of pharmaceutical manufacturing processes. Over the past decade, there have been significant advancements in science and engineering to support the implementation of continuous pharmaceutical manufacturing. These investments along with the adoption of the quality-by-design (QbD) paradigm for pharmaceutical development and the advancement of process analytical technology (PAT) for designing, analyzing, and controlling manufacturing have progressed the scientific and regulatory readiness for continuous manufacturing. The FDA supports the implementation of continuous manufacturing using science- and risk-based approaches.

Three trials tested related hypotheses regarding genotype-informed dosing strategies for anticoagulants yet arrived at different results. Careful assessment of these trials can help to reframe the dialogue regarding evidentiary assessment of coumarin pharmacogenetics.

It is widely agreed that pharmaceuticals should be manufactured to a high standard of quality, because they are frequently critical to human health, and because the consequences of quality problems such as sub-potency, lack of sterility, or product mix-ups can be so devastating. Nevertheless, the U.

Whether new versions of currently marketed, or de novo biological drugs, biobetters are products specifically designed to maximize clinical performance. Performance optimization may include, among other improvements, enhanced targeting and delivery, increased activity and half-life, and reduced immunogenicity. Thus, it is critical that such products are developed efficiently and quickly, to allow patients access to drugs that provide maximum clinical benefits.

Alzheimer’s disease (AD) and Parkinson’s disease (PD) pose significant challenges for successful development of new therapies, with anextremely high drug trial failure rate and yet no approved disease modifying drugs available. Given the magnitude of the challenges, it has become clear that larger collaborations and multi-partner joint efforts, pooling resources and expertise,are required for theadvancement of methods and tools that are critically needed to support drug development studies. Critical Path Institute’s Coalition against Major Diseases was formed in 2008, at a time prior to the era of public private partnerships, with the mission of streamlining and de-risking drug development for AD and PD. Since its origin, the consortium has achieved several milestones including development of consensus data standards for AD and PD, a unified clinical trial database comprised of placebo data from AD therapeutic trials and regulatory endorsement of drug development tools. In addition, the consortium is progressing strongly on other initiatives, with ongoing regulatory interactions. The coalition held its annual conference at the U.S. Food and Drug Administration, where diverse stakeholders including industry, academic experts, government agency representatives, patient advocacy organizations and regulators gathered together to share their accomplishments and focus on the needs of the future. The current landscape was emphasized with focus on the need to expand the precompetitive space and enhance data sharing globally.

The potential medical applications of microarrays have generated much excitement, and some skepticism, within the biomedical community. Some researchers have suggested that within the decade microarrays will be routinely used in the selection, assessment, and quality control of the best drugs for pharmaceutical development, as well as for disease diagnosis and for monitoring desired and adverse outcomes of therapeutic interventions. Realizing this potential will be a challenge for the whole scientific community, as breakthroughs that show great promise at the bench often fail to meet the requirements of clinicians and regulatory scientists. The development of a cooperative framework among regulators, product sponsors, and technology experts will be essential for realizing the revolutionary promise that microarrays hold for drug development, regulatory science, medical practice and public health.

Pharmacogenetics (PGt) and now the more global term, pharmacogenomics (PGx), have come to the forefront after an evolutionary period of more than 30 years. Several transforming events in the past 5 years, not the least of which was the completion of the human genome sequence in 2001, have created an expectation that genetic and genomic information will produce sweeping changes in the practice of medicine and the prescribing of drugs. The almost daily press reports of new gene discoveries lend credence to the argument that personal genetic/genomic profiles will have a tremendous impact on health by the year 2010. This vision has not been without naysayers; however, we believe that the central issue is not whether PGt- or PGx-guided drug prescriptions will happen, but when and how.

This review of FDA’s Drug Trials Snapshots Program evaluates the sex-specific findings reported as part of the approval process for all cardiovascular drugs that the FDA approved in 2015.

Successful development of future targeted therapies will require the flexibility to rapidly evaluate combination regimens involving new targeted agents in a single development program. The FDA has therefore developed draft guidance on drug co-development.

Improving the science of drug development and regulation is important in fulfilling the public health mission of the US Food and Drug Administration (FDA). A decade on from the launch of the Critical Path Initiative, the FDA's Center for Drug Evaluation and Research (CDER) is now participating in more than 20 science-driven consortia to achieve this goal.

The US Food and Drug Administration (FDA) has directed considerable effort towards modernizing its regulatory processes over the past decade to address the challenges in the drug development sector. Through partnerships and input from stakeholders, multiple initiatives are under way, many projects have been launched, several have resulted in tangible results, and many are ongoing and under discussion. We are learning that collaborative efforts can better inform and leverage existing knowledge, that the challenges of data sharing and intellectual property can be overcome, and that there is wide interest in partnering to address key public health regulatory science issues. It is crucial that we continue to build on these initial efforts to facilitate drug development.

There is broad agreement among health-care stakeholders that more must be done to ensure that patients have timely access to new and innovative medicines. Assuming that industry will continue to develop such medicines at a sustainable rate, regulators and payers become the gatekeepers. Regulators, starting in the late 1980s/early 1990s, and, more recently, payers have implemented a variety of early-access pathways or initiatives, and this practice is continuing even today. This article describes the specific approaches that have been taken in four economically developed regions, reviews their success rates, and suggests possible new directions.

The US Food and Drug Administration Safety and Innovation Act (FDASIA) was signed on 9 July 2012. This law created a new "breakthrough therapy" (BT) designation program for investigational drugs and biologics intended to treat a serious disease and having "preliminary clinical evidence [that] indicates that the drug may demonstrate substantial clinical improvement over existing therapies on one or more clinically significant endpoints."(1) Many questions have been posed about the impact of this new program on drug development.

There have been ongoing concerns about the safety of the diabetes drugs containing rosiglitazone (Avandia, Avandaryl, and Avandamet) — a thiazolidinedione antidiabetic agent indicated as an adjunct to diet and exercise to improve glycemic control in adults with type 2 diabetes mellitus. In 2007, a meta-analysis of controlled clinical trials found increases in the risk of myocardial infarction and a near-significant increased risk of death from cardiovascular causes when rosiglitazone was compared with placebo or with standard diabetes drugs.1 Following an advisory committee meeting held in July 2007, the U.S. Food and Drug Administration (FDA) added information about the possibility . . .

Janet Woodcock is the Director of the US FDA’s Center for Drug Evaluation and Research. Dr Woodcock has held various positions within the FDA’s Office of the Commissioner from October 2003 until 1 April, 2008, as Deputy Commissioner and Chief Medical Officer, Deputy Commissioner for Operations and Chief Operating Officer and Director of the Critical Path Programs. She oversaw scientific and medical regulatory operations for the FDA. Dr Woodcock served as Director of the Center for Drug Evaluation and Research at the FDA from 1994 to 2005. She previously served in other positions at the FDA including Director of the Office of Therapeutics Research and Review and Acting Deputy Director of the Center for Biologics Evaluation and Research. Dr Woodcock received her MD from Northwestern Medical School (IL, USA), and completed further training and held teaching appointments at the Pennsylvania State University (PA, USA)and the University of California in San Francisco (CA, USA). She joined the FDA in 1986.

Obesity is associated with hyperinsulinemia and elevated concentrations of tumor necrosis factor-alpha (TNF-alpha) in adipose tissue. TNF-alpha has been implicated as an inducer of the synthesis of plasminogen activator inhibitor-1 (PAI-1), the primary physiological inhibitor of fibrinolysis, mediated by plasminogen activators in cultured adipocytes. To identify mechanism(s) through which TNF-alpha induces PAI-1, 3T3-L1 preadipocytes were differentiated into adipocytes and exposed to TNF-alpha for 24 h. TNF-alpha selectively increased the synthesis of PAI-1 without increasing activity of plasminogen activators. Both superoxide (generated by xanthine oxidase plus hypoxanthine) and hydrogen peroxide were potent inducers of PAI-1, and hydroxyl radical scavengers completely abolished the TNF-alpha induction of PAI-1. Exposure of adipocytes to TNF-alpha or insulin alone over 5 days increased PAI-1 production. These agonists exert synergistic effects. Results obtained suggest that TNF-alpha stimulates PAI-1 production by adipocytes, an effect potentiated by insulin, and that adipocyte generation of reactive oxygen centered radicals mediates the induction of PAI-1 production by TNF-alpha. Because induction of PAI-1 by TNF-alpha is potentiated synergistically by insulin, both agonists appear likely to contribute to the impairment of fibrinolytic system capacity typical in obese, hyperinsulinemic patients.

Multiple new genomic diagnostic tests are currently under development. Given the lack of an efficient translational infrastructure, it is not clear how, or whether, robust evidence for their clinical value will be generated.

Long-term blockade of nitric oxide synthesis with Nω-nitro-L-arginine methyl ester (L-NAME) induces cardiac perivascular fibrosis in rats. Its relationship to expression of angiogenic growth factors and capillary network remodeling is not understood. This study was designed to determine whether capillary proliferation and angiogenic growth factor regulation occur in response to L-NAME. Three groups of rats were studied: C, control; L1, L-NAME 13 mg/kg/day; L2, 130 mg/kg/day. One and eight weeks later the hearts were removed and subjected to morphometric analysis and analysis of gene expressions of molecules related to angiogenesis. Arterial hypertension was observed within 8 weeks in the L1 and L2 groups compared with control. After 1 week immunohistochemical assays demonstrated basic fibroblast growth factor (bFGF) in the arteriolar media. Northern blot analysis revealed increase in bFGF and transforming growth factor-β (TGF-β) mRNA during this period. At 8 weeks arteriolar medial thickening and perivascular fibrosis were seen microscopically in the L1 and L2 groups, which were accompanied by only a modest remodeling of capillary network due to increase in venular or intermediate capillary portions. Concomitantly immunoreactivity for vascular endothelial growth factor (VEGF) and TGF-β were detected in perivascular area. These results suggest that (1) blockade of NO synthesis induces expression of angiogenic growth factors as well as vessel wall remodeling, and (2) TGF-β may counteract angiogenic growth factors and limit subsequent alterations in capillary network remodeling.