Evaluation of Outcome Prediction of Flow Diversion for Intracranial Aneurysms

BACKGROUND AND PURPOSE

Identifying and predicting which aneurysms are likely to quickly occlude and which ones are likely to remain open following treatment with flow-diverting devices is important to develop optimal patient management strategies. The purpose of this study was to evaluate predictions based on computational fluid dynamics models using the elastase rabbit aneurysm model.

MATERIALS AND METHODS

A series of 13 aneurysms created in rabbits were treated with flow diverters, and outcomes were angiographically assessed at 8 weeks' follow-up. Computational fluid dynamics models were constructed from pretreatment 3D rotational angiograms and Doppler ultrasound flow velocity measurements. Postimplantation mean aneurysm inflow rate and flow velocity were used to prospectively predict aneurysm occlusion blinded to the actual outcomes. Specifically, if both variables were below their corresponding thresholds, fast occlusion was predicted, while if one of them was above the threshold, slow or incomplete occlusion was predicted.

RESULTS

Of the 13 aneurysms included, 8 were incompletely occluded 8 weeks after treatment, and 5 were completely occluded. A total of 10 computational fluid dynamics-based predictions agreed with the angiographic outcome, reaching 77% accuracy, 80% sensitivity, and 75% specificity. Posttreatment mean velocity alone was able to achieve the same predictive power as the combination of inflow rate and velocity.

CONCLUSIONS

Subject-specific computational fluid dynamics models of the hemodynamic conditions created immediately after implantation of flow-diverting devices in experimental aneurysms created in rabbits are capable of prospectively predicting, with a reasonable accuracy, which aneurysms will completely occlude and which ones will remain incompletely occluded.

Regional Aneurysm Wall Enhancement is Affected by Local Hemodynamics: A 7T MRI Study

BACKGROUND AND PURPOSE

Aneurysm wall enhancement has been proposed as a biomarker for inflammation and instability. However, the mechanisms of aneurysm wall enhancement remain unclear. We used 7T MR imaging to determine the effect of flow in different regions of the wall.

MATERIALS AND METHODS

Twenty-three intracranial aneurysms imaged with 7T MR imaging and 3D angiography were studied with computational fluid dynamics. Local flow conditions were compared between aneurysm wall enhancement and nonenhanced regions. Aneurysm wall enhancement regions were subdivided according to their location on the aneurysm and relative to the inflow and were further compared.

RESULTS

On average, wall shear stress was lower in enhanced than in nonenhanced regions (P = .05). Aneurysm wall enhancement regions at the neck had higher wall shear stress gradients (P = .05) with lower oscillations (P = .05) than nonenhanced regions. In contrast, aneurysm wall enhancement regions at the aneurysm body had lower wall shear stress (P = .01) and wall shear stress gradients (P = .008) than nonenhanced regions. Aneurysm wall enhancement regions far from the inflow had lower wall shear stress (P = .006) than nonenhanced regions, while aneurysm wall enhancement regions close to the inflow tended to have higher wall shear stress than the nonenhanced regions, but this association was not significant.

CONCLUSIONS

Aneurysm wall enhancement regions tend to have lower wall shear stress than nonenhanced regions of the same aneurysm. Moreover, the association between flow conditions and aneurysm wall enhancement seems to depend on the location of the region on the aneurysm sac. Regions at the neck and close to the inflow tend to be exposed to higher wall shear stress and wall shear stress gradients. Regions at the body, dome, or far from the inflow tend to be exposed to uniformly low wall shear stress and have more aneurysm wall enhancement.

Abstract P2-14-05: Can an internal surgical adhesive facilitate drain-free mastectomy and reduce overall invasiveness?-A prospective, randomized, controlled, multicenter non-inferiority trial

Introduction: Mastectomy closure without drains has many potential advantages. Flap fixation techniques have shown to be an effective alternative to drains. This study tested the non-inferiority of a surgical adhesive in overall invasiveness compared to standard wound closure with drains. Methods: This trial (ClinicalTrials.gov Identifier: NCT02958449) recruited seventy-seven patients undergoing eighty-four mastectomies +/- SLNB (n=84) at eleven international centers. Procedures were prospectively randomized to standard wound closure with drains (SWC; n=41) or wound closure without drains using a high strength lysine-based adhesive named TissuGlu® (TG; n= 43). The primary outcome measured assessed overall invasiveness using the number of post-operative clinical interventions, including drain removals and needle aspirations. Secondary endpoints included total wound drainage, cumulative days of treatment, days to drain removal and wound healing related complications. A patient questionnaire evaluating quality of life measures was also administered. Results: Subjects in the TissuGlu® group required significantly fewer post-operative clinical interventions (1.25 ± 1.39 TG vs. 2.03 ± 1.45 SWC, p = <.0001) compared to the Control group and had fewer cumulative days of treatment (defined as days of drains being in place and / or days on which an aspiration occurred; 2.14 ± 4.15 TG vs. 5.76 ± 4.02 SWC, p = <0.0001). Presence of a drain was associated with significantly higher pain and lower mobility scores. Conclusion: The study demonstrates that flap fixation with this adhesive can permit drain-free mastectomy closure, reducing overall invasiveness and patient morbidity.

Citation Format: Eichler C, Paepke S, Ohlinger R, Mathias W, Scheffen I, Lux M, Hadad S, Kiernan T, Whisker L, Kaushik M, King P. Can an internal surgical adhesive facilitate drain-free mastectomy and reduce overall invasiveness?-A prospective, randomized, controlled, multicenter non-inferiority trial [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-14-05.

Abstract P2-08-02: Interaction of PIK3CA mutation subclasses with response to preoperative treatment with the PI3K inhibitor pictilisib in patients with estrogen receptor-positive breast cancer

Background: Although preclinical data suggest that combining PI3K inhibitors with endocrine therapy may overcome resistance, results from randomized clinical trials have failed to identify a subgroup of patients that derive a substantial benefit. This preoperative window study assessed whether adding the PI3K inhibitor pictilisib can increase the anti-tumor effects of anastrozole in primary breast cancer and aimed to identify the most appropriate patient population for combination therapy.

Methods: In this randomized, open-label, phase 2 study, 167 postmenopausal women with newly diagnosed, operable, ER-positive, HER2-negative breast cancers were recruited. Participants were randomly allocated (2:1, favoring the combination) to two-weeks of preoperative treatment with anastrozole 1 mg once daily or the combination of anastrozole 1mg with pictilisib 260 mg once daily. The primary endpoint was inhibition of tumor cell proliferation, as measured by change in Ki-67 protein expression between tumor samples taken before and at the end of treatment. Secondary endpoints include induction of apoptosis (Caspase3) and safety. Comprehensive biomarkers analyses included targeted NGS of a comprehensive cancer panel of >400 genes (Ampliseq Comprehensive Cancer panel), copy number variation analyses, and pre- and post-treatment reverse-phase protein arrays (RPPA) and RNA profiling (NanoString nCounter platform).

Results:There was significantly greater geometric mean Ki67 suppression of 82.5% (90% CI, 78.3%-85.8%) for the combination vs 70.7% (61.0%-78.0%) for anastrozole [geometric mean ratio (combination/ anastrozole) 0.60 (0.58-0.85);p=0.01]. Higher baseline Ki67, Luminal B status and/or negative PR status were associated with increased benefit from adding pictilisib. A significant interaction was observed between PIK3CA mutation subtypes [helical domain mutations (HD), kinase domain mutations (KD), wildtype (WT)] and mean Ki67 suppression; the combination/anastrozole geometric mean ratio of Ki67 suppression was 0.48 (0.27-0.84; p=0.02) for patients with HD mutations and 0.63 (0.39–1.0; p=0.05) for patients with PIK3Ca WT, compared to 1.17 (0.57–2.41; p=0.64) for patients with KD mutations. This was largely due to patients with HD mutations showing a particularly poor response to anastrozole alone [mean Ki67 suppression 53.9% (9.5%-76.5%)], that was reversed by the addition of pictilisib [mean Ki-67 suppression 78.1% (71.0%-83.4%)]. On the other hand, patients with KD mutations responded well to anastrozole alone [mean Ki-67 suppression 77.7% (57.0%-88.4%)] and showed no benefit from the addition of pictilisib [mean Ki-67 suppression 73.9% (59.8%-83.0%)]. There was no significant difference in induction of apoptosis between treatment groups. Comprehensive pre- and post-treatment biomarkers analyses will be presented.

Conclusions: Adding pictilisib to anastrozole significantly increases the anti-proliferative response to preoperative treatment with anastrozole. A significant interaction was observed between PIK3CA mutation subtypes, with patients with helical domain mutations showing a particularly poor response to anastrozole alone that was reversed by the addition of pictilisib.

Citation Format: Schmid P, Pinder S, Wheatley D, Zummit C, Macaskill EJ, Hu J, Price R, Bundred N, Hadad S, Shia A, Sarker S-J, Lim L, Mousa K, O'Brien C, Wilson TR, Lackner MR, Gendreau S, Gazinska P, Korbie D, Trau M, Mainwaring P, Thompson A, Purushotham A. Interaction of PIK3CA mutation subclasses with response to preoperative treatment with the PI3K inhibitor pictilisib in patients with estrogen receptor-positive breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-08-02.

Prophylactic central neck dissection for papillary thyroid cancer (Br J Surg 2013; 100: 410–418)

The Editors welcome topical correspondence from readers relating to articles published in the Journal. Responses should be sent electronically via the BJS website (www.bjs.co.uk). All letters will be reviewed and, if approved, appear on the website. A selection of these will be edited and published in the Journal. Letters must be no more than 250 words in length

Comparison of 30-day, 90-day and in-hospital postoperative mortality for eight different cancer types (Br J Surg 2012; 99: 1149-1154)

No

The Effect of Neoadjuvant Metformin on Breast Cancer Related Genes Clinical Trial – A Preliminary Result

Other authoring group: Dougal Adamson, Lee Baker, Douglas C Brown, Sally Chalmers, Amanda Degabriele, Janet Flinn, Kenneth Fowler, Avril Gunning, Grahame Hardie, Julie Lindsay, Gillian Little, Denis McLean, Robert Murdoch, Colin Purdie, Marta Reis, Valerie Walker.IntroductionMetformin, used in the treatment of diabetes for 50 years, has been linked to a reduced incidence of breast cancer and to an enhanced pathological response when administered concurrent with neoadjuvant chemotherapy. It has been postulated that the anti-neoplastic effect of metformin is through activation of AMP-activated protein Kinase (AMPK). The aim of this open label, randomised clinical trial was to investigate the effect of neoadjuvant metformin on gene expression in primary breast cancer.MethodsNon-diabetic women with histologically proven, operable, primary invasive breast cancer of ≥1cm in size were offered the trial following regional Research Ethics Committee approval.The trial had 2 arms, A and B: in arm A (8 patients), patients had core biopsies at three time points: one at presentation; one after a week of no treatment (internal control); and a further biopsy at the time of definitive surgery after at least 2 weeks of metformin. In trial arm B (47 patients), patients had core biopsies at two time points: one before randomisation to either take metformin or not, and one at the time of definitive breast surgery. Metformin was given as 500mg o.d. orally for one week, increased to 1g b.d. orally for at least another week and until the day prior to excisional breast surgery.RNA was extracted from formalin fixed cores and examined using a Disease-Specific Array for breast cancer on an Affymetrix platform (ALMAC Diagnostics Group, Craigavon, UK). Subsequent confirmatory polymerase chain reaction and immunohistochemistry techniques were used to examine the histological material.ResultsType of results expected:[Change of target gene expression in response to neoadjuvant metformin; symptomatic drug toxicities; potential for therapeutic effects of metformin in non-diabetic patients in vivo.]Results from the first arm:The triplet of core biopsies from 6/8 (75%) of the A arm patients passed the GeneGhip QC and data integrity assessment. Patients were 41-65 (mean: 53) years, with IDC NST, grade II-III, and all ER positive. 270 genes were differentially expressed significantly by wounding, and 63 by metformin. Among the genes significantly over-expressed by metformin were AMPK-beta and PI3K; and those down regulated by metformin were AMPK-gamma and ADCY1. Samples from the B arm patients are in analysis.ConclusionThe gene expression changes identified in response to neoadjuvant metformin suggest that metformin improves DNA damage recognition and repair and regulates cancer cell metabolism. These results suggest mechanisms by which metformin could be efficacious in the treatment of breast cancer.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 3145.

αB-crystallin, vimentin and increased p53 expression levels in breast cancer is associated with poor prognosis

Abstract #5070

Background: Previous studies have identified αB-crystallin as a marker of poor prognosis for breast cancer and have suggested that it is an excellent marker for tumours of basal origin. Increased expression of αB-crystallin has been associated with anchorage-independent growth and metastasis leading to the suggestion that αB-crystallin is an oncoprotein. We have considered whether the αB-crystallin binding proteins, vimentin and HSP27 also show a similar association with poor prognosis. We also investigated whether either HSP27 phosphorylation HSP27 or p53 expression could be associated with αB-crystallin expression.
 Methods: Tissue Micro Arrays of 0.6x0.6mm cores of 205 breast cancers were stained with antibodies to αB-crystallin, vimentin, p53 (antibodies DO1, FP3), HSP27 (antibody ERD5) and HSP27 82P. The levels of protein expressions were then compared with clinical and pathological parameters.
 Results: The expression of αB-crystallin was positively associated with vimentin (P<0.001 Fisher's exact test (FET)). We have confirmed that αB-crystallin expression is linked to a low expression of the estrogen receptor and reduced survival (P<0.001 (FET), P=0.002 Kaplan Meier Log Rank (KM) respectively). Vimentin expression was similarly associated with estrogen receptor (ER) negative cancers and poor survival (P <0.001 (FET), P= 0.002 (KM Log Rank) respectively). Low expression of HSP27 resulted in poor three-year survival (P=0.007 (KM Log Rank)), but longer-term survival was unaffected (P=0.09 (KM Log Rank)). In contrast to αB-crystallin, low expression of HSP27 was associated with ER and progesterone receptor (PGR) negativity (P<0.001 (FET), P=0.001 (FET)). HSP27 82P similarly resulted in poor three-year survival (P=0.01 (KM Log Rank)) compared with longer-term survival (P=0.05 (KM Log Rank)). In samples positive for either αB-crystallin or vimentin, a strong association with increased p53 expression (p53 antibodies: DO1(P<0.001 (FET)) and FP3(P<0.001 (FET))) was found.
 Conclusions: The increased expression of the protein chaperone, αB-crystallin was linked with reduced survival as well as it's binding partner, vimentin. We found that within this patient subgroup, there was an increased level of p53. The potential functional significance of this interaction for metastasis will be discussed in the context of other predictive markers for breast cancer. A similar association was not found for HSP27 expression.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 5070.

Pharmacokinetics of fluphenazine, a highly lipophilic drug, estimated from a pulse dose of a stable isotopomer in dogs at steady state

The potential utility of a pulse dose of a deuterium-labeled isotopomer (FLU-D(4)) in elucidating the pharmacokinetics of fluphenazine (FLU) at steady state was investigated in dogs. The single-dose oral pharmacokinetics of FLU in dogs were established. After resting the dogs for 3 weeks, the animals were dosed to steady state with oral FLU administered at 12-h intervals. Following 15 doses, one dose of FLU was replaced by a pulse dose of FLU-D(4), after which dosing with FLU was resumed. FLU and FLU-D(4) plasma concentrations were determined by tandem mass spectrometry. Comparable estimates of apparent oral clearance were calculated from (i) a single dose of FLU, (ii) a pulse dose of FLU-D(4), and (iii) over a dosing interval at steady state. Average steady-state plasma concentrations were reliably predictable from a pulse dose of FLU-D(4).

Home intravenous antibiotic treatment for febrile episodes in immune-compromised pediatric patients

The purpose of this work was to assess the feasibility of home intravenous antibiotic treatment (HIAT) for febrile episodes in immune-compromised (neutropenic, splenectomized), low-risk pediatric patients. Thirty hematology-oncology patients who presented to our emergency room from January 1993 to January 1995 and who suffered from a febrile episode and were considered at low risk for septic complications were immediately discharged on HIAT. Patients were followed for at least 3 weeks after recovery. Patients and parents were retrospectively questioned about adverse effects and about their degree of satisfaction with home treatment. Patients who required hospitalization during this period were considered unresponsive to HIAT and were analyzed for causes and adverse effects. Thirteen out of 60 (22%) febrile episodes, or eight out of 42 (19%) episodes of fever and neutropenia eventually led to hospitalization. Pseudomonas species infections were associated with the highest rate of unresponsiveness (88%). A central venous catheter infection developed in two cases following HIAT (two cases out of 640 days of therapy). No other complications were identified. No infection-related morbidity was observed. Patients and parents were highly satisfied with HIAT and wanted to use it again, if necessary. Immediate discharge on HIAT for low-risk pediatric immune-compromised patients suffering from a febrile episode is feasible, safe, and well accepted by patients and families. Patients who are found to have Pseudomonas infections should probably be hospitalized. Our results are preliminary and must be confirmed by a prospective, randomized trial before definite recommendations can be made.

Pharmacokinetic analysis and antiepileptic activity of two new isomers of N-valproyl glycinamide

Valproyl glycinamide (TV 1901-VPGD) is a new antiepileptic drug, which is currently undergoing clinical trials. The present study explored the pharmacokinetics and pharmacodynamics (anticonvulsant activity and neurotoxicity) of two new isomers of valproyl glycinamide: valnoctyl glycinamide (VCGD) and diisopropylacetyl (DIGD). Both VCGD and DIGD showed anticonvulsant activity and a safety margin in mice similar to those of VPGD. Following i.v. administration (556 mg) to six dogs, VCGD had a clearance (Cl) value of 3.8 +/- 1.1 Lh-1 (mean +/- SD), a volume of distribution (Vss) of 15 +/- 2 L, and a half-life (t1/2) of 1.9 +/- 0.3 h. DIGD had Cl, Vss, and t1/2 values of 10 +/- 0.8 Lh-1, 19 +/- 3 L, and 1.6 +/- 0.2 h, respectively. Neither VCGD nor DIGD operated as chemical drug delivery systems (CDDSs) of glycine, valnoctic acid, or diisopropyl acetic acid and both showed antiepileptic profiles different from that of valproic acid (VPA). Both glycinamides were biotransformed to their glycine analogues with similar fractions metabolized (fm): 59 +/- 5% (VCGD) and 62 +/- 15% (DIGD). The two glycine metabolites, valnoctyl glycine (VCGA) and diisopropylacetyl glycine (DIGA), were also administered to the same dogs in order to calculate the above fm values. Both VCGA and DIGA had higher Cl and lower Vss values than VCGD and DIGD and therefore their mean t1/2 values were 0.43 +/- 0.02 and 0.30 +/- 0.07 h, respectively. VCGA and DIGA were excreted mainly intact in the urine, with fractions excreted unchanged (fe) of 60 +/- 9 and 55 +/- 7%, respectively. The improved pharmacokinetic profile of VCGD and DIGD relative to their glycine analogues may explain the similarity of their anticonvulsant activity to that of valproyl glycinamide. The current study demonstrates the benefit of the structure-pharmacokinetic-pharmacodynamic relationship (SPPR) approach in developing and selecting a potent antiepileptic compound in intact animals based not only on its intrinsic pharmacodynamic activity but also on its improved pharmacokinetic profile.

Pharmacokinetic analysis and antiepileptic activity of tetra-methylcyclopropane analogues of valpromide

PURPOSE

The described structure pharmacokinetic pharmacodynamic relationships (SPPR) study explored the utilization of tetramethylcyclopropane analogues of valpromide (VPD), or tetramethylcyclopropane carboxamide derivatives of valproic acid (VPA) as new antiepileptics.

METHODS

The study was carried out by investigating the pharmacokinetics in dogs and pharmacodynamics (anticonvulsant activity and neurotoxicity) of the following three cyclopropane analogues of VPD: 2,2,3,3-tetramethylcyclopropane carboxamide (TMCD), N-methyl TMCD (M-TMCD) and N-[(2,2,3,3-tetramethylcyclopropyl)carbonyl]-glycinamide (TMC-GLD).

RESULTS

The three investigated compounds showed a good anticonvulsant profile in mice and rats due to the fact that they were metabolically stable VPD analogues which were not biotransformed to their nonactive acid, 2,2,3,3-tetramethylcyclopropane carboxylic acid (TMCA). M-TMCD was metabolized to TMCD and TMC-GLD underwent partial biotransformation to its glycine analogue N-[(2,2,3,3-tetramethylcyclopropyl)carbonyl]-glycine (TMC-GLN). Unlike TMC-GLN, the above mentioned amides had low clearance and a relatively long half life.

CONCLUSIONS

In contrast to VPD which is biotransformed to VPA, the aforementioned cyclopropane derivatives were found to be stable to amide-acid biotransformation. TMCD and M-TMCD show that cyclic analogues of VPD, like its aliphatic isomers, must have either two substitutions at the beta position to the carbonyl, such as in the case of TMCD, or a substitution in the alpha and in the beta positions like in the VPD isomer, valnoctamide (VCD). This paper discusses the antiepileptic potential of tetramethylcyclopropane analogues of VPD which are in animal models more potent than VPA and may be non-teratogenic and non-hepatotoxic.

Pharmacokinetic analysis and antiepileptic activity of N-valproyl derivatives of GABA and glycine

PURPOSE

To explore the possibility of utilizing valproyl derivatives of GABA and glycine as new antiepileptics by using the structure pharmacokinetic-pharmacodynamic relationship (SPPR) approach.

METHODS

The pharmacokinetics and pharmacodynamics (anticonvulsant activity and neurotoxicity) of the following four conjugation products of valproic acid (VPA), glycine and GABA were investigated: valproyl glycine, valproyl glycinamide, valproyl GABA and valproyl gabamide.

RESULTS

Only valproyl glycinamide showed a good anticonvulsant profile in both mice and rats due to its better pharmacokinetic profile. Valproyl glycinamide was more potent than one of the major antiepileptic agents--VPA and showed a better margin between activity and neurotoxicity. Valproyl glycine and valproyl GABA were partially excreted unchanged in the urine (fe = 50% and 34%, respectively), while the urinary metabolites of the amide derivatives were valproyl glycine and valproyl GABA.

CONCLUSIONS

The four investigated valproyl derivatives did not operate as chemical drug delivery systems (CDDS) of glycine or GABA, but acted rather as drugs on their own. The current study demonstrates the benefit of the SPPR approach in developing and selecting a potent antiepileptic compound in intact animals based not only on its intrinsic pharmacodynamic activity, but also on its better pharmacokinetic profile.

Comparative pharmacokinetic and pharmacodynamic analysis of phthaloyl glycine derivatives with potential antiepileptic activity

Glycine, in addition to GABA, is one of the most important neurotransmitter amino acids. The described structure pharmacokinetic pharmacodynamic relationships (SPPR) study explored the possibility of utilizing phthaloyl derivatives of glycine as new antiepileptics. This was carried out by investigating the pharmacokinetics and pharmacodynamics (anticonvulsant activity and neurotoxicity) of the following four phthalimide derivatives: phthaloyl glycine, phthaloyl glycinamide, N,N-diethyl phthaloyl glycinamide and N,N-diisopropyl phthaloyl glycinamide. Phthaloyl glycine did not demonstrate anticonvulsant activity, possibly because of its poor pharmacokinetics, high clearance, low volume of distribution and short half life. The three glycinamide derivatives showed anticonvulsant activity and had better pharmacokinetic profiles, longer half life and mean residence time, than phthaloyl glycine. Phthaloyl glycinamide was more potent than one of the major antiepileptic agents--valproic acid and showed a better margin between activity and neurotoxicity. The four investigated phthaloyl glycine derivatives did not operate as chemical drug delivery systems (CDDS) of glycine, but acted rather as drugs on their own. Phthaloyl glycine was excreted unchanged in the urine while the urinary metabolites of the glycinamide derivatives were phthaloyl glycine and phthaloyl glycinamide. In this analogous series of phthalimide derivatives, minor chemical changes affected dramatically the compounds' pharmacokinetics. The current study demonstrates the benefit of the SPPR approach in developing and selecting a potent antiepileptic compound in intact animals based not only on its intrinsic pharmacodynamic activity, but also on its better pharmacokinetic profile.(ABSTRACT TRUNCATED AT 250 WORDS)

Can we develop improved derivatives of valproic acid?

Valproic acid is one of the major antiepileptic drugs. In animal models, valproate showed less anticonvulsant potency than the other three established antiepileptic drugs: phenobarbital, phenytoin and carbamazepine. In addition, two major side-effects, teratogenicity and hepatotoxicity, have been associated with valproate therapy. Due to the above and the shortage of new antiepileptic drugs there is a substantial need to develop improved derivatives of valproate. This paper analyses three kinds of valproate derivatives: valpromide, the primary amide of valproate, and its analogues; monoester prodrugs of valproate and an active metabolite of valproate, 2-n-propyl-2-pentenoate. The comparative evaluation was carried out by pharmacokinetic and pharmacodynamic analyses in animals. From the data accumulated so far, we can conclude that 2-n-propyl-2-pentenoate and/or a valpromide isomer, which does not undergo amide-acid biotransformation and preferably is not an epoxide hydrolase inhibitor, may prove to be improved derivatives of the parent compound valproic acid.

Pharmacokinetic analysis of two new sustained-release products of diltiazem designed for twice- and once-daily treatment

The pharmacokinetics of two new sustained-release (SR) products of diltiazem, Dilapress 120 mg tablets and Dilapress 240 mg tablets, was analysed and characterized in three different studies, in comparison to the following diltiazem SR formulations: Cardizem Retard, Cardizem SR, and Cardizem CD. Dilapress 120, designated for twice-daily dosing, was found to be bioequivalent to Cardizem SR and to Cardizem Retard with mean (+/- SD) relative bioavailability values of 99 +/- 27% and 113 +/- 38%, respectively. Dilapress 240, designed for once-a-day treatment, was found to have a slower absorption rate than Cardizem SR and its extent of absorption was 56 +/- 19% relative to that of Cardizem SR. However, the bioavailability of Dilapress 240 relative to that of Cardizem CD was 118 +/- 46%, indicating that the bioavailability of Cardizem CD relative to that of Cardizem SR was only 54 +/- 29%. Diltiazem is partially available due to a saturable liver first-pass effect. A high dose of Cardizem SR may partially escape this first-pass effect and, thus, achieve a higher extent of absorption than a slower SR product. Consequently, SR products of diltiazem designed for once-daily treatment may not reach the saturation stage in the liver first-pass effect process that diltiazem is susceptible to. Consequently, a twice-daily SR product of diltiazem cannot serve as a reference for extent of absorption assessments of a once-daily SR product.

Pharmacokinetic analysis and anticonvulsant activity of two polyesteric prodrugs of valproic acid

The pharmacokinetics of the following two polyesteric prodrugs of valproic acid (VPA) have been investigated: 1,4-butanediol divalproate (BDV) and glyceryl trivalproate (GTV). In addition, the anticonvulsant activity of these compounds has been evaluated and compared to that of VPA and valpromide (VPD). Valproic acid, and its two esteric derivatives were administered intravenously to six dogs at an equivalent dose (400 mg VPA) and their pharmacokinetics investigated. In the case of BDV, the biotransformation to VPA was complete, but in the case of GTV, it was only partial. Of the two investigated esteric prodrugs of VPA, only BDV demonstrated anticonvulsant activity and showed less neurotoxicity than VPA and VPD, and therefore had a better protective index. The anticonvulsant activity is explained on pharmacokinetic and pharmacodynamic grounds due to its complete conversion to VPA and the possible synergism in anticonvulsant activity between VPA and 1,4-butanediol.

Pharmacokinetic analysis of ester prodrugs of valproic acid

The pharmacokinetics of five monoester prodrugs of valproic acid (VPA) were investigated: propyl valproate (P-VPA), butyl valproate (B-VPA), isobutyl valproate (IB-VPA), isoamyl valproate (IA-VPA), and hexyl valproate (H-VPA). In addition, the anticonvulsant activity of these compounds was evaluated and compared with that of VPA and valpromide (VPD). The pharmacokinetics of VPA and its five ester derivatives were determined after intravenous administration of equivalent doses (400 mg of VPA) to six dogs. The five ester prodrugs of VPA were biotransformed to VPA; the biotransformation was complete for P-VPA, B-VPA, and H-VPA but was only partial for IB-VPA and IA-VPA. Because of the rapid conversion of the prodrugs to the parent drug, levels of VPA in plasma after administration of the prodrugs peaked at 6-26 min after dosing and did not yield an in vivo sustained-release dosage profile. Of the five ester prodrugs of VPA, only P-VPA demonstrated anticonvulsant activity. P-VPA also was less neurotoxic than VPA and VPD; therefore, it has a better protective index.

Pharmacokinetic analysis of the structural requirements for forming "stable" analogues of valpromide

The following valpromide (VPD) analogues were synthesized and their structure-pharmacokinetic relationships explored: 3-ethyl pentanamide (EPD), methylneopentylacetamide (MND), 1-methyl cyclohexanecarboxamide (MCD), cycloheptanecarboxamide (CHD), and t-butylacetamide (TBD). Two aliphatic (EPD and MND) and two cyclic amides (MCD and CHD) underwent complete or partial conversion to their corresponding acids. The only amide found in this study to be "stable" to the amide-acid biotransformation was TBD. It also had the lowest clearance and the longest half-life and mean residence time. Unlike the other investigated amides, TBD contained two substitutions of two methyl moieties at the beta position of its chemical structure. A "stable" valpromide analogue must have either two substitutions at the beta position, such as in the case of TBD, or a substitution in the alpha and beta positions, such as in the case of the VPD isomer valnoctamide (VCD). This paper discusses the antiepileptic potential of stable VPD analogues which may be more potent and less teratogenic than their biotransformed isomers.