Predictive value of ectopic HORMAD1 tumor expression for high-dose platinum-based chemotherapy benefit in patients with high-risk HER2-negative breast cancer

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Background: The meiotic DNA break regulator HORMAD1 is aberrantly expressed in many cancers and is associated with increased genomic instability. The susceptibility of HORMAD1 expressing tumors to agents targeting DNA damage repair (DDR) pathways is poorly understood since clinical data within the context of a randomized clinical trial (RCT) is lacking. Here, we retrospectively studied HORMAD1 expression as a putative predictive biomarker in an RCT for benefit of adjuvant high-dose platinum-based chemotherapy (HDCT) with autologous stem cell support in patients with high-risk HER2-negative early breast cancer (BC). Methods: Patients with stage III BC participated in an RCT comparing HDCT to conventional chemotherapy (CDCT; Rodenhuis et all, NEJM, 2003; Steenbruggen et all, JAMA Oncol, 2020). We studied the subgroup with HER2-negative BC for whom tumor BRCA1-like classification was previously determined using a validated DNA comparative genomic hybridization algorithm (Vollebergh et all, BCR, 2014). Tumor HORMAD1 expression was determined on FFPE samples using RNAscope, an RNA in situ hybridization method, and classified as negative (no expression) or positive (any expression detected). Results: For 195/246 (79.3%) HER2-negative patients treated according to protocol, HORMAD1 RNAscope status was available; dropout was due to absence or insufficient quality of tumor specimens. HORMAD1 positivity was enriched in triple-negative breast cancer (TNBC) (23/47; 48.9%). Furthermore, in all HER2-negative BCs, HORMAD1 positivity (45/195; 23.1%) was associated with age ≤40 years, histological grade III, <10 positive lymph nodes, breast-conserving surgery, BRCA1-like profile, and tumor-infiltrating lymphocytes (TILs) >10%. Such association, although not significant, was also observed within TNBC. During a median follow-up of 20.3 years, 124 (63.6%) recurrences and 115 deaths (59.0%) occurred. The prognostic effect of HORMAD1 positivity on overall survival (OS) varied with follow-up time and was borderline significant at 10 years and significant thereafter (10-year: adjusted (adj.) HR 0.47, 95% CI 0.21-1.04; 15-year: adj. HR 0.25, 95% CI 0.07-0.91). Benefit on RFS from HDCT over CDCT was stronger in patients with HORMAD1-positive tumors (adj. HR 0.18, 95% CI 0.06-0.54) than in patients with HORMAD1-negative tumors (adj. HR 0.69, 95% CI 0.46-1.02) (P-interaction = 0.02). Similar results were observed for OS. Conclusions: In this retrospective sub study of 195 patients with high-risk HER2-negative BC participating in an RCT, tumor HORMAD1 expression is predictive for benefit of high-dose platinum-based chemotherapy. Our observations are consistent with the prior observations that HORMAD1 expression is associated with genomic instability and impaired DDR pathways. Further research is warranted to validate our findings. Clinical trial information: NCT03087409.

Prognostic impact of recurrence score, endocrine response and clinical-pathological factors in high-risk luminal breast cancer: Results from the WSG-ADAPT HR+/HER2- chemotherapy trial

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Background: In HR+/HER2- N0-1 early BC, postmenopausal patients (pts) with RS™ > 25 and a substantial proportion of premenopausal pts seem to benefit from addition of adjuvant chemotherapy (CT) to endocrine therapy (ET). However, the magnitude of absolute benefit from this treatment intensification seems to depend on clinical-pathological and biological prognostic factors. For the first time, we present outcome from the CT part of the prospective phase III WSG-ADAPT HR+/HER- trial combining both static (RS in baseline core biopsy (CB) and dynamic (Ki67 response) biomarkers to optimize adjuvant therapy in luminal EBC. Methods: Pts with clinically high-risk HR+/HER2- EBC (cT2-4 OR clinically N+ OR G3 OR Ki67>15%) were initially treated by 3 (+/-1) weeks of standard ET (postmenopausal: mostly AI; premenopausal: TAM) before surgery or sequential CB. Pts with cN2-3 or G3/Ki67>40% were randomized directly to the CT trial. pN0-1 pts with RS0-11 OR RS12-25/ET-response (central Ki67postendocrine<10%) received ET alone; the remaining high-risk cohort was randomized to the CT trial: (neo)adjuvant dose-dense CT (4xPaclitaxelà4xEC q2w vs. 8xNab-Paclitaxel q1wà4xEC q2w) followed by ET. Primary endpoint is efficacy comparison of CT schedules for survival; secondary endpoints reported here involve impacts of key prognostic factors on survival. Kaplan-Meier and Cox proportional hazard models were used to estimate survival curves and hazard ratios. For this analysis, subgroups free of selection bias by RS/ET-response were defined. Results: 5625 pts were screened and 4621 (ITT) entered the trial. After 4.9y median follow-up, higher baseline and post-endocrine Ki-67 levels were associated with poorer iDFS (both p < 0.001). In the CT cohort (n = 2331), higher RS, nodal status, and tumor size were generally associated with poorer iDFS. However, iDFS differed between N1 and N0 status only among younger pts (<50 years). In pts with >4 positive LN (n = 390), lower RS was associated with improved iDFS (RS0-11 vs RS > 25: plog-rank= 0.016, 5y-iDFS 90% vs. 64%). In pts with RS > 25 (n = 965), low Ki67postendocrine, N0 status, and c/pT1 status were associated with improved iDFS. In particular, ET-responders had higher 5y-iDFS (84%) than ET-non-responders (77%; plog-rank= 0.040). Younger patients (<50 years old) with N0-1 RS 12-25/ ET-non-responders treated by CT had non-significantly poorer 5-year iDFS (89%) compared to those with ET-response treated by ET only (92%) (plog-rank= 0.249). Conclusion: First results from the prospective high risk cohort from a large prospective phase III ADAPT trial provide evidence for good prognosis in some pts with >4 positive LN and e.g. low RS. Moreover combination of lower post-endocrine Ki-67 and limited tumor burden may be a promising criterion for CT de-escalation strategies even in patients with high RS. Clinical trial information: NCT01779206.

Immune cell composition and functional marker dynamics from multiplexed immunohistochemistry to predict response to neoadjuvant chemotherapy in the WSG-ADAPT-TN trial

BACKGROUND

The association of early changes in the immune infiltrate during neoadjuvant chemotherapy (NACT) with pathological complete response (pCR) in triple-negative breast cancer (TNBC) remains unexplored.

METHODS

Multiplexed immunohistochemistry was performed in matched tumor biopsies obtained at baseline and after 3 weeks of NACT from 66 patients from the West German Study Group Adjuvant Dynamic Marker-Adjusted Personalized Therapy Trial Optimizing Risk Assessment and Therapy Response Prediction in Early Breast Cancer - Triple Negative Breast Cancer (WSG-ADAPT-TN) trial. Association between CD4, CD8, CD73, T cells, PD1-positive CD4 and CD8 cells, and PDL1 levels in stroma and/or tumor at baseline, week 3 and 3-week change with pCR was evaluated with univariable logistic regression.

RESULTS

Compared with no change in immune cell composition and functional markers, transition from 'cold' to 'hot' (below-median and above-median marker level at baseline, respectively) suggested higher pCR rates for PD1-positive CD4 (tumor: OR=1.55, 95% CI 0.45 to 5.42; stroma: OR=2.65, 95% CI 0.65 to 10.71) and PD1-positive CD8 infiltrates (tumor: OR=1.77, 95% CI 0.60 to 5.20; stroma: OR=1.25, 95% CI 0.41 to 3.84; tumor+stroma: OR=1.62, 95% CI 0.51 to 5.12). No pCR was observed after 'hot-to-cold' transition in PD1-positive CD8 cells. pCR rates appeared lower after hot-to-cold transitions in T cells (tumor: OR=0.26, 95% CI 0.03 to 2.34; stroma: OR=0.35, 95% CI 0.04 to 3.25; tumor+stroma: OR=0.00, 95% CI 0.00 to 1.04) and PD1-positive CD4 cells (tumor: OR=0.60, 95% CI 0.11 to 3.35; stroma: OR=0.22, 95% CI 0.03 to 1.92; tumor+stroma: OR=0.32, 95% CI 0.04 to 2.94). Higher pCR rates collated with 'altered' distribution (levels below-median and above-median in tumor and stroma, respectively) of T cell (OR=3.50, 95% CI 0.84 to 14.56) and PD1-positive CD4 cells (OR=4.50, 95% CI 1.01 to 20.14).

CONCLUSION

Our exploratory findings indicate that comprehensive analysis of early immune infiltrate dynamics complements currently investigated predictive markers for pCR and may have a potential to improve guidance for individualized de-escalation/escalation strategies in TNBC.

Health-related quality of life of long-term advanced melanoma survivors treated with anti-CTLA-4 immune checkpoint inhibition compared to matched controls

BACKGROUND

Checkpoint inhibitors have changed overall survival for patients with advanced melanoma. However, there is a lack of data on health-related quality of life (HRQoL) of long-term advanced melanoma survivors, years after treatment. Therefore, we evaluated HRQoL in long-term advanced melanoma survivors and compared the study outcomes with matched controls without cancer.

MATERIAL AND METHODS

Ipilimumab-treated advanced melanoma survivors without evidence of disease and without subsequent systemic therapy for a minimum of two years following last administration of ipilimumab were eligible for this study. The European Organization for Research and Treatment of Cancer quality of life questionnaire Core 30 (EORTC QLQ-C30), the Multidimensional Fatigue Inventory (MFI), the Hospital Anxiety and Depression Scale (HADS), and the Functional Assessment of Cancer Therapy-Melanoma questionnaire (FACT-M) were administered. Controls were individually matched for age, gender, and educational status. Outcomes of survivors and controls were compared using generalized estimating equations, and differences were interpreted as clinically relevant according to published guidelines.

RESULTS

A total of 89 survivors and 265 controls were analyzed in this study. After a median follow-up of 39 (range, 17-121) months, survivors scored significantly lower on physical (83.7 vs. 89.8, difference (diff) = -5.80, p=.005), role (83.5 vs. 90, diff = -5.97, p=.02), cognitive (83.7 vs. 91.9, diff = -8.05, p=.001), and social functioning (86.5 vs. 95.1, diff = -8.49, p= <.001) and had a higher symptom burden of fatigue (23.0 vs. 15.5, diff = 7.48, p=.004), dyspnea (13.3 vs. 6.7, diff = 6.47 p=.02), diarrhea (7.9 vs. 4.0, diff = 3.78, p=.04), and financial impact (10.5 vs. 2.5, diff = 8.07, p=.001) than matched controls. Group differences were indicated as clinically relevant.

DISCUSSION

Compared to matched controls, long-term advanced melanoma survivors had overall worse functioning scores, more physical symptoms, and financial difficulties. These data may contribute to the development of appropriate survivorship care.

Novel peptide inhibitor of dipeptidyl peptidase IV (Tyr-Pro-D-Ala-NH2) with anti-inflammatory activity in the mouse models of colitis

Protease inhibition has become a new possible approach in the inflammatory bowel disease (IBD) therapy. A serine exopeptidase, dipeptidyl peptidase IV (DPP IV) is responsible for inactivation of incretin hormone, glucagon-like peptide 2 (GLP-2), a potent stimulator of intestinal epithelium regeneration and growth. Recently we showed that the novel peptide analog of endomorphin-2, EMDB-1 (Tyr-Pro-D-ClPhe-Phe-NH₂) is a potent blocker of DPP IV and exhibits an anti-inflammatory activity in vivo. The aim of this study was to design, synthesize and characterize the therapeutic activity and mechanism of action of a series of novel EMDB-1 analogs. The inhibitory potential of all peptides was evaluated using the fluorometric screening assay employing Gly-Pro-Aminomethylcoumarin (AMC) to measure DPP IV activity. Consequently, one compound, namely DI-1 was selected and its therapeutic activity evaluated using mouse models of experimental colitis (induced by TNBS and DSS). Macro- and microscopic score, ulcer score, colonic wall thickness as well as myeloperoxidase activity were measured. We showed that DI-1 blocks DPP IV in vitro (IC₅₀ = 0.76 ± 0.04 nM) and attenuates acute, semichronic and relapsing TNBS- as well as DSS-induced colitis in mice after topical administration. Its anti-inflammatory action is associated with the increase of colonic GLP-2 but not GLP2 receptor or DPP IV expression. Our results validate DPP IV as a pharmacological target for the anti-IBD drugs and its inhibitors, such as DI-1, have the potential to become valuable anti-inflammatory therapeutics.

Long-term prognosis of young breast cancer patients (≤40 years) who did not receive adjuvant systemic treatment: protocol for the PARADIGM initiative cohort study

INTRODUCTION

Currently used tools for breast cancer prognostication and prediction may not adequately reflect a young patient's prognosis or likely treatment benefit because they were not adequately validated in young patients. Since breast cancers diagnosed at a young age are considered prognostically unfavourable, many treatment guidelines recommend adjuvant systemic treatment for all young patients. Patients cured by locoregional treatment alone are, therefore, overtreated. Lack of prognosticators for young breast cancer patients represents an unmet medical need and has led to the initiation of the PAtients with bReAst cancer DIaGnosed preMenopausally (PARADIGM) initiative. Our aim is to reduce overtreatment of women diagnosed with breast cancer aged ≤40 years.

METHODS AND ANALYSIS

All young, adjuvant systemic treatment naive breast cancer patients, who had no prior malignancy and were diagnosed between 1989 and 2000, were identified using the population based Netherlands Cancer Registry (n=3525). Archival tumour tissues were retrieved through linkage with the Dutch nationwide pathology registry. Tissue slides will be digitalised and placed on an online image database platform for clinicopathological revision by an international team of breast pathologists. Immunohistochemical subtype will be assessed using tissue microarrays. Tumour RNA will be isolated and subjected to next-generation sequencing. Differences in gene expression found between patients with a favourable and those with a less favourable prognosis will be used to establish a prognostic classifier, using the triple negative patients as proof of principle.

ETHICS AND DISSEMINATION

Observational data from the Netherlands Cancer Registry and left over archival patient material are used. Therefore, the Dutch law on Research Involving Human Subjects Act (WMO) is not applicable. The PARADIGM study received a 'non-WMO' declaration from the Medical Ethics Committee of the Netherlands Cancer Institute - Antoni van Leeuwenhoek hospital, waiving individual patient consent. All data and material used are stored in a coded way. Study results will be presented at international (breast cancer) conferences and published in peer-reviewed, open-access journals.

Abstract P2-09-16: How population-based data complement trial data in the adjuvant endocrine treatment of ER+/HER2+ breast cancers

Background

This study is part of the Netherlands Breast Cancer Project, initiated to address research questions that are unlikely answered by future randomized controlled trials (RCT). Here we investigated whether aromatase inhibitors (AI) are superior over tamoxifen (TAM), in the treatment of Estrogen Receptor (ER) positive Human Epidermal growth factor Receptor 2 (HER2) positive breast cancer, using treatment and outcome data from the population based Netherlands Cancer Registry (NCR). RCTs showed superiority of AI over TAM in postmenopausal ER+/HER2+ patients while a (non-significant) suggestion for worse outcome was observed among premenopausal patients treated with AI in the SOFT/TEXT trial. Perimenopausal women were not considered in these trials.

Methods

Dutch women without a prior malignancy, diagnosed between 2005-2007 with an ER+/HER2+, endocrine treated, non-metastatic, invasive breast cancer, were identified through the NCR and followed until 2013. Since data on menopausal status were lacking, we used age at diagnosis as a proxy to categorize patients as premenopausal (≤45 years), perimenopausal (45-55 years) and postmenopausal (&gt;55 years). A time-dependent variable was calculated indicating whether AI treatment was given for &gt;50% (denoted AI treated) vs. &lt;50% (denoted TAM treated) of endocrine treatment duration. Recurrence-free survival (RFS) and overall survival (OS) were assessed using an extended Kaplan-Meier survival estimator and Cox proportional hazards regression. Hazard Ratios (HR) for the TAM/AI comparison, were adjusted for chemotherapy, trastuzumab, age at diagnosis, lymph node status, grade, clinical T stage, and ovarian ablation.

Results

We included 1158 patients: 326 pre-, 306 peri- and 526 postmenopausal. Of these, 229 received TAM and 929 AI. During follow-up, 239 RFS and 184 OS events were observed. In the TAM treated group, 56 RFS and 45 OS events were observed, in the AI treated group 183 RFS and 139 RFS events were observed respectively.

No differences in RFS were observed comparing AI to TAM treated patients in the premenopausal (HR 1.33; 95% CI 0.71-2.49; P=0.378) and postmenopausal (HR 0.84, 95%CI 0.54-1.32; P=0.456) group. However, perimenopausal patients benefitted significantly from AI compared with TAM (HR 0.50; 95% CI 0.27-0.95). Results were similar for OS: no significant benefit from AI when compared to TAM in pre- (HR 1.41; 95% CI 0.62-3.19; P=0.408) and postmenopausal (HR 0.75; 95% CI 0.47-1.22; P=0.245) patients while perimenopausal patients derived significant benefit from AI treatment (HR 0.42; 95% CI 0.20-0.85; P=0.016).

Conclusion

In this population based cohort study we observed superiority for AI over TAM in the treatment of ER+/HER2+ perimenopausal patients. Data were suggestive in favor of AI when compared to TAM for postmenopausal patients while an indication of worse outcome with AI was seen in premenopausal patients, consistent with results of the SOFT/TEXT trial. Although we used age as a proxy for menopausal status, our results are consistent with previous RCTs. Population based data may therefore provide a reliable source of information when new RCTs might not be feasible anymore.

Citation Format: Dackus GMHE, Jozwiak K, Sonke GS, Van der Wall E, Van Diest PJ, Hauptmann M, Siesling S, Linn SC. How population-based data complement trial data in the adjuvant endocrine treatment of ER+/HER2+ breast cancers [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P2-09-16.

Abstract P5-08-07: The long-term prognosis of breast cancers patients diagnosed ≤40 years in the absence of adjuvant systemic therapy

This abstract was withdrawn by the authors.

Subchronic administration of (R,S)-ketamine induces ketamine ring hydroxylation in Wistar rats

Subchronic administration of (R,S)-ketamine, (R,S)-Ket, is used in the treatment of neuropathic pain, in particular Complex Regional Pain Syndrome, but the effect of this protocol on the metabolism of (R,S)-Ket is unknown. In this study, daily administration of a low dose of (R,S)-Ket for 14-days to Wistar rats was conducted to determine the impact of sub-chronic dosing on the pharmacokinetics of (R,S)-Ket and its major metabolites. The data indicate that, relative to a single administration of (R,S)-Ket, subchronic administration resulted in increased clearance of (R,S)-Ket and the N-demethylated metabolite norketamine measured as elimination half-life (t1/2) and decreased plasma concentrations of these compounds. Subchronic administration produced a slight decrease in t1/2 and an increase in plasma concentration of the major metabolite, (2S,6S;2R,6R)-hydroxynorketamine, and produced significant increases in the plasma concentrations of the (2S,6R;2R,6S)-hydroxynorketamine and (2S,4R;2R,4S)-hydroxynorketamine metabolites. The metabolism of (R,S)-Ket predominately occurs via two microsomal enzyme-mediated pathways: (R,S)-Ket⇒(R,S)-norketamine⇒(2S,6S;2R,6R)-hydroxynorketamine and (2S,4R;2R,4S)-hydroxynorketamine and the (R,S)-Ket⇒(2S,6R;2R,6S)-hydroxyketamine⇒(2S,6R;2R,6S)-hydroxynorketamine and (2S,6S;2R,6R)-hydroxynorketamine. The results indicate that the activity of both metabolic pathways are increased by subchronic administration of (R,S)-Ket producing new metabolite patterns and potential differences in clinical effects.

Recent progress in understanding of structure, ligand interactions and the mechanism of activation of the β₂-adrenergic receptor

The understanding of β₂-adrenergic receptor (β₂AR) interactions with ligands as well as the mechanism of receptor activation changed radically from 2007, when the first crystallographic structure of the receptor was reported. Since then numerous crystallographic studies described interactions with all main classes of β₂AR ligands and with G proteins, which provided a great insight into the molecular structure of the receptor. However, molecular mechanisms of receptor activations remain to be determined. Functional research supported the concept of ligand-directed signaling at β-adrenoceptors. Agonist can activate alternative signaling pathways with different capacities and trigger cellular effects. It indicates that agonists nominally belonging to the same class may bind to and/or stabilize different active conformations of the receptor which are selectively recognized by signaling proteins in the allosteric manner.

{Beta}2-adrenergic receptor agonists inhibit the proliferation of 1321N1 astrocytoma cells

Astrocytomas and glioblastomas have been particularly difficult to treat and refractory to chemotherapy. However, significant evidence has been presented that demonstrates a decrease in astrocytoma cell proliferation subsequent to an increase in cAMP levels. The 1321N1 astrocytoma cell line, as well as other astrocytomas and glioblastomas, expresses β(2)-adrenergic receptors (β(2)-ARs) that are coupled to G(s) activation and consequent cAMP production. Experiments were conducted to determine whether the β(2)-AR agonist (R,R')-fenoterol and other β(2)-AR agonists could attenuate mitogenesis and, if so, by what mechanism. Receptor binding studies were conducted to characterize β(2)-AR found in 1321N1 and U118 cell membranes. In addition, cells were incubated with (R,R')-fenoterol and analogs to determine their ability to stimulate intracellular cAMP accumulation and inhibit [(3)H]thymidine incorporation into the cells. 1321N1 cells contain significant levels of β(2)-AR as determined by receptor binding. (R,R')-fenoterol and other β(2)-AR agonists, as well as forskolin, stimulated cAMP accumulation in a dose-dependent manner. Accumulation of cAMP induced a decrease in [(3)H]thymidine incorporation. There was a correlation between concentration required to stimulate cAMP accumulation and inhibit [(3)H]thymidine incorporation. U118 cells have a reduced number of β(2)-ARs and a concomitant reduction in the ability of β(2)-AR agonists to inhibit cell proliferation. These studies demonstrate the efficacy of β(2)-AR agonists for inhibition of growth of the astrocytoma cell lines. Because a significant portion of brain tumors contain β(2)-ARs to a greater extent than whole brain, (R,R')-fenoterol, or some analog, may be useful in the treatment of brain tumors after biopsy to determine β(2)-AR expression.

Updating parameters of the chicken processing line model

A mathematical model of chicken processing that quantitatively describes the transmission of Campylobacter on chicken carcasses from slaughter to chicken meat product has been developed in Nauta et al. (2005). This model was quantified with expert judgment. Recent availability of data allows updating parameters of the model to better describe processes observed in slaughterhouses. We propose Bayesian updating as a suitable technique to update expert judgment with microbiological data. Berrang and Dickens's data are used to demonstrate performance of this method in updating parameters of the chicken processing line model.

Determination and modelling of stereoselective interactions of ligands with drug transporters: a key dimension in the understanding of drug disposition

1. Stereochemistry is an important dimension in pharmacology and plays a role in every aspect of the pharmacological fate of chiral xenobiotics. This includes small molecule-drug transporter binding. 2. This paper reviews the reported stereoselectivities of substrate and inhibitor interactions with P-glycoprotein and the organic cation transporter obtained using standard functional and binding studies, as well as data obtained from online cellular membrane affinity chromatography studies. 3. The use of stereochemical data in quantitative structure-activity relationship (QSAR) and pharmacophore modelling is also addressed as is the effect of ignoring the fact that small molecule-drug transporter interactions take place in three-dimensional and asymmetric space.

Enantioselective binding to the human organic cation transporter-1 (hOCT1) determined using an immobilized hOCT1 liquid chromatographic stationary phase

A liquid chromatography stationary phase containing immobilized membranes obtained from a cell line that expresses the human organic cation transporter (hOCT1-IAM) has been used to study the binding of the enantiomers of propranolol, atenolol, pseudoephedrine, and alpha-methylbenzylamine to the immobilized hOCT1. Frontal displacement chromatography was used to determine the binding affinities (K(d) values), and the data demonstrate that there was an enantioselective difference in the K(d) values of the enantiomers of propranolol, atenolol, and pseudoephedrine, while alpha-methylbenzylamine did not significantly bind to the transporter. Competitive inhibition studies with the cell line used to create the chromatographic column demonstrated that, for the enantiomers of propranolol, the ratio of the chromatographically determined K(d) values [K(d (+)-(R)-propranolol)/K(d (-)-(S)-propranolol) = 2.98] reflected an enantioselective difference in the functional activity of the two enantiomers [IC(50 (+)-(R)-propranolol)/IC(50 (-)-(S)-propranolol) = 2.75]. The chromatographically determined K(d) values were used to construct an initial pharmacophore which contains a hydrogen bond donating site that appears to be responsible for the observed enantioselectivity.