Efficacy and safety of garadacimab, a factor XIIa inhibitor for hereditary angioedema prevention (VANGUARD): a global, multicentre, randomised, double-blind, placebo-controlled, phase 3 trial.

BACKGROUND: Hereditary angioedema is a rare and potentially life-threatening genetic disease that is associated with kallikrein-kinin system dysregulation. Garadacimab (CSL312), a novel, fully-human monoclonal antibody that inhibits activated factor XII (FXIIa), is being studied for the prevention of hereditary angioedema attacks. The aim of this study was to evaluate the efficacy and safety of once-monthly subcutaneous administrations of garadacimab as prophylaxis for hereditary angioedema. METHODS: VANGUARD was a pivotal, multicentre, randomised, double-blind, placebo-controlled, phase 3 trial that recruited patients (aged ≥12 years) with type I or type II hereditary angioedema across seven countries (Canada, Germany, Hungary, Israel, Japan, the Netherlands, and the USA). Eligible patients were randomly assigned (3:2) to receive garadacimab or placebo for 6 months (182 days) by an interactive response technology (IRT) system. Randomisation was stratified by age (≤17 years vs >17 years) and baseline attack rate (1 to <3 attacks per month vs ≥3 attacks per month) for the adult group. The randomisation list and code were kept by the IRT provider during the study, with no access by site staff and funding representatives. All patients and investigational site staff, and representatives from the funder (or their delegates) with direct interaction with the study sites or patients, were masked to treatment assignment in a double-blind fashion. Randomly assigned patients received a 400-mg loading dose of subcutaneous garadacimab as two 200-mg injections or volume-matched placebo on day 1 of the treatment period, followed by five additional self-administered (or caregiver-administered) monthly doses of 200-mg subcutaneous garadacimab or volume-matched placebo. The primary endpoint was the investigator-assessed time-normalised number of hereditary angioedema attacks (number of hereditary angioedema attacks per month) during the 6-month treatment period (day 1 to day 182). Safety was evaluated in patients who received at least one dose of garadacimab or placebo. The study is registered with the EU Clinical Trials Register, 2020-000570-25 and ClinicalTrials.gov, NCT04656418. FINDINGS: Between Jan 27, 2021, and June 7, 2022, we screened 80 patients, 76 of whom were eligible to enter the run-in period of the study. Of 65 eligible patients with type I or type II hereditary angioedema, 39 were randomly assigned to garadacimab and 26 to placebo. One patient was randomly assigned in error and did not enter the treatment period (no dose of study drug received), resulting in 39 patients assigned to garadacimab and 25 patients assigned to placebo being included. 38 (59%) of 64 participants were female and 26 (41%) were male. 55 (86%) of 64 participants were White, six (9%) were Asian (Japanese), one (2%) was Black or African American, one (2%) was Native Hawaiian or Other Pacific Islander, and one (2%) was listed as other. During the 6-month treatment period (day 1 to day 182), the mean number of investigator-confirmed hereditary angioedema attacks per month was significantly lower in the garadacimab group (0·27, 95% CI 0·05 to 0·49) than in the placebo group (2·01, 1·44 to 2·57; p<0·0001), corresponding to a percentage difference in means of -87% (95% CI -96 to -58; p<0·0001). The median number of hereditary angioedema attacks per month was 0 (IQR 0·00-0·31) for garadacimab and 1·35 (1·00-3·20) for placebo. The most common treatment-emergent adverse events were upper-respiratory tract infections, nasopharyngitis, and headaches. FXIIa inhibition was not associated with an increased risk of bleeding or thromboembolic events. INTERPRETATION: Monthly garadacimab administration significantly reduced hereditary angioedema attacks in patients aged 12 years and older compared with placebo and had a favourable safety profile. Our results support the use of garadacimab as a potential prophylactic therapy for the treatment of hereditary angioedema in adolescents and adults. FUNDING: CSL Behring.

Prophylactic use of an anti-activated factor XII monoclonal antibody, garadacimab, for patients with C1-esterase inhibitor-deficient hereditary angioedema: a randomised, double-blind, placebo-controlled, phase 2 trial.

BACKGROUND: Hereditary angioedema is associated with dysregulation of the kallikrein-kinin system. Factor XII (FXII) is a key initiator of the kallikrein-kinin system, which produces bradykinin, a central mediator of angioedema. Garadacimab (CSL Behring) is a first-in-class, fully human, immunoglobulin G4 monoclonal antibody targeting activated FXII, intended to prevent attacks in patients with C1-esterase inhibitor-deficient hereditary angioedema (HAE-C1-INH). We aimed to investigate garadacimab as a treatment every 4 weeks for patients with HAE-C1-INH. METHODS: In this double-blind, placebo-controlled, phase 2 study, patients with HAE-C1-INH were recruited from 12 research centres in Canada, Germany, Israel, and the USA. Eligible patients were aged 18-65 years and must have had at least four attacks of any severity over a consecutive 2-month period during the 3 months before screening or initiation of previous hereditary angioedema prophylaxis. After a run-in period of 4-8 weeks, patients were randomly assigned (1:1:1:1), using an interactive response technology via block randomisation (block sizes of 1-4), to either placebo or 75 mg, 200 mg, or 600 mg garadacimab. Patients were given an initial intravenous loading dose, and then, on day 6 and every 4 weeks for 12 weeks, they were given a subcutaneous dose of their allocated treatment. The primary endpoint was the number of monthly attacks in the intention-to-treat population (defined as all patients who underwent screening, provided consent, and were assigned to treatment) during the 12-week subcutaneous administration period assessed in the 200 mg and 600 mg garadacimab groups versus placebo. Safety was assessed in all patients who received at least one dose or partial dose of study treatment. This study is registered with ClinicalTrials.gov, NCT03712228. FINDINGS: Between Oct 29, 2018, and Aug 28, 2019, 54 patients were screened, of whom 32 were randomly assigned to either placebo (n=8) or 75 mg (n=9), 200 mg (n=8), or 600 mg (n=7) garadacimab. The median age was 39·5 years (28·0-52·5) and 18 (56%) of 32 patients were female and 14 (34%) were male. The median number of monthly attacks during the 12-week subcutaneous treatment period was 4·6 (IQR 3·1-5·0) with placebo, 0·0 (0·0-0·4) with 75 mg garadacimab, 0·0 (0·0-0·0) with 200 mg garadacimab, and 0·3 (0·0-0·7) with 600 mg garadacimab. Compared with placebo, the rate of attacks was significantly reduced with garadacimab at 200 mg (reduced by 100% [95% CI 98-101]; p=0·0002) and 600 mg (reduced by 93% [54-110]; p=0·0003). No serious adverse events, deaths, or adverse events of special interest (anaphylaxis, thromboembolic events, and bleeding events) were observed. INTERPRETATION: Garadacimab 200 mg and 600 mg every 4 weeks significantly reduced the number of monthly attacks versus placebo and was well tolerated during the study. Garadacimab is an efficacious, subcutaneous prophylaxis in patients with HAE-C1-INH and warrants phase 3 evaluation. FUNDING: CSL Behring.

Efficacy, pharmacokinetics, and safety of subcutaneous C1-esterase inhibitor as prophylaxis in Japanese patients with hereditary angioedema: Results of a Phase 3 study.

BACKGROUND: Hereditary angioedema (HAE) is a rare and potentially life-threatening genetic disorder characterized by recurrent attacks of angioedema. HAE types I and II result from deficient or dysfunctional C1-esterase inhibitor (C1-INH). This Phase 3 study assessed the efficacy, pharmacokinetics (PK), and safety of subcutaneous (SC) C1-INH in Japanese patients with HAE. METHODS: The prospective, open-label, multicenter, single-arm Phase 3 study recruited patients with HAE types I or II to an initial run-in period, followed by a 16-week treatment period where patients received 60 IU/kg C1-INH (SC) twice weekly. The two primary endpoints were the time-normalized number of HAE attacks per month and C1-INH functional activity at Week 16. RESULTS: Nine patients entered the treatment period and completed the study. Treatment with C1-INH (SC) significantly reduced the mean monthly attack rate from 3.7 during the run-in period to 0.3 during treatment (exploratory p value of within-patient comparison = 0.004). After the last dose of C1-INH (SC) at Week 16, the mean trough concentration of C1-INH was 59.8%, and the mean area under the plasma concentration-time curve to the end of the dosing period and to the last sample were 5317.1 and 13,091.5 h•%, respectively. During the study, there were no deaths, serious adverse events, or adverse events leading to study discontinuation. CONCLUSIONS: C1-INH (SC) (60 IU/kg twice weekly) was efficacious and well tolerated as a prophylaxis against HAE attacks in Japanese patients with HAE types I or II, which was supported by the increased and maintained C1-INH functional activity. EudraCT Number 2019-003921-99; JapicCTI-205273.

Long-term safety and efficacy of subcutaneous C1-inhibitor in older patients with hereditary angioedema.

BACKGROUND: Patients aged 65 years and older with hereditary angioedema (HAE) owing to C1-inhibitor (C1-INH) deficiency may have an altered response to treatment and are at higher risk for treatment-related adverse events (AEs) because of comorbidities and polypharmacy. OBJECTIVE: To investigate the safety and efficacy of subcutaneous C1 esterase inhibitor (C1-INH) in patients aged 65 years and older treated in an open-label extension of a phase 3 trial. METHODS: Eligible patients (≥4 attacks for more than 2 consecutive months) were randomized to receive twice-weekly subcutaneous C1-INH with a dosage of 40 IU/kg or 60 IU/kg for 52 to 140 weeks. Safety end points and efficacy outcomes were evaluated for patients aged 65 years and above and younger than 65 years. RESULTS: Of the 126 patients treated, 10 were 65 years and older (mean age [range], 68 [65-72 years]). A total of 8 of 10 patients had multiple comorbidities, and 6 of these 10 patients were taking more than 5 non-HAE-related drugs concomitantly. AEs occurring in more than 1 patient included injection site bruising (n = 2, related), injection site pain (n = 2, related), urinary tract infection (n = 2, unrelated), and diarrhea (n = 2, unrelated). No thromboembolic events or cases of anaphylaxis were reported. Two patients aged 65 years and older experienced unrelated serious AEs (dehydration and hypokalemia in 1 and pneumonia and an HAE attack leading to hospitalization in another). A total of 6 of 9 evaluable patients were responders, with a greater than or equal to 50% reduction in HAE attacks vs prestudy; 6 of 10 patients had less than 1 attack over 4 weeks and 3 were attack-free (median attack rate, 0.52 attacks per month). CONCLUSION: Subcutaneous C1-INH was well-tolerated and effective in the management of HAE in patients aged 65 years and older with multiple comorbid conditions and polypharmacy.

Long-acting recombinant coagulation factor IX albumin fusion protein (rIX-FP) in hemophilia B: results of a phase 3 trial.

A global phase 3 study evaluated the pharmacokinetics, efficacy, and safety of recombinant fusion protein linking coagulation factor IX with albumin (rIX-FP) in 63 previously treated male patients (12-61 years) with severe hemophilia B (factor IX [FIX] activity ≤2%). The study included 2 groups: group 1 patients received routine prophylaxis once every 7 days for 26 weeks, followed by either 7-, 10-, or 14-day prophylaxis regimen for a mean of 50, 38, or 51 weeks, respectively; group 2 patients received on-demand treatment of bleeding episodes for 26 weeks and then switched to a 7-day prophylaxis regimen for a mean of 45 weeks. The mean terminal half-life of rIX-FP was 102 hours, 4.3-fold longer than previous FIX treatment. Patients maintained a mean trough of 20 and 12 IU/dL FIX activity on prophylaxis with rIX-FP 40 IU/kg weekly and 75 IU/kg every 2 weeks, respectively. There was 100% reduction in median annualized spontaneous bleeding rate (AsBR) and 100% resolution of target joints when subjects switched from on-demand to prophylaxis treatment with rIX-FP (P< .0001). The median AsBR was 0.00 for all prophylaxis regimens. Overall, 98.6% of bleeding episodes were treated successfully, including 93.6% that were treated with a single injection. No patient developed an inhibitor, and no safety concerns were identified. These results indicate rIX-FP is safe and effective for preventing and treating bleeding episodes in patients with hemophilia B at dosing regimens of 40 IU/kg weekly and 75 IU/kg every 2 weeks. This trial was registered at www.clinicaltrials.gov as #NCT0101496274.

Subcutaneous C1-esterase inhibitor to prevent hereditary angioedema attacks: Safety findings from the COMPACT trial.

BACKGROUND: The first subcutaneous (SC) C1-esterase inhibitor concentrate (C1-INH) was approved by the U.S. Food and Drug Administration in June 2017 as routine prophylaxis to prevent hereditary angioedema attacks in adolescents and adults at a dose of 60 IU/kg twice weekly based on the phase III Clinical Study for Optimal Management of Preventing Angioedema With Low-volume Subcutaneous C1-Inhibitor Replacement Therapy (COMPACT) trial. OBJECTIVE: This article aimed to evaluate the relationship of the C1-INH (SC) dose regimens tested in the COMPACT trial (40 IU/kg and 60 IU/kg twice weekly) and the occurrence of adverse events (AEs). METHODS: Patients were instructed to record any AEs in their e-diary daily. Safety and tolerability were assessed based on reported AEs, including injection-site reactions (ISRs); unsolicited AEs (AEs other than ISRs); serious AEs; thrombotic, thromboembolic, anaphylactic, hypersensitivity, sepsis, and bacteremia events; inhibitory antibodies to C1-INH; and clinically significant abnormalities in laboratory assessments. Information on ISRs was specifically solicited. RESULTS: No relationship between the dose of C1-INH (SC) and the incidence of ISRs or unsolicited AEs was observed. The proportion of injections followed by at least one ISR was 12% with C1-INH (SC) 40 IU/kg versus 5% with 60 IU/kg and 6% with placebo. No ISRs were serious or led to treatment discontinuation, and all resolved. There were no anaphylaxis, thromboembolic, sepsis, or bacteremia events reported during treatment with C1-INH (SC). All hypersensitivity AEs were nonserious, and the majority were assessed as being unrelated to treatment. No inhibitory antibodies to C1-INH were observed. CONCLUSION: C1-INH (SC) is safe and well tolerated with no dose-dependent safety concerns, as demonstrated in the COMPACT trial.Clinical trial NCT01912456, www.clinicaltrials.gov.

Safety and pharmacokinetics of a novel recombinant fusion protein linking coagulation factor IX with albumin (rIX-FP) in hemophilia B patients.

A recombinant fusion protein linking coagulation factor IX (FIX) with human albumin (rIX-FP) has been developed to facilitate hemophilia B treatment by less frequent FIX dosing. This first-in-human dose-escalation trial in 25 previously treated subjects with hemophilia B (FIX ≤ 2 IU/dL) examined the safety and pharmacokinetics of 25, 50, and 75 IU/kg rIX-FP. Patients in the 50-IU/kg cohort underwent a comparative pharmacokinetics assessment with their previous FIX product (plasma-derived or recombinant). No allergic reactions or inhibitors were observed. Four mild, possibly treatment-related adverse events were reported. In the 50-IU/kg cohort (13 subjects), the mean half-life of rIX-FP was 92 hours, more than 5 times longer than the subjects' previous FIX product. After 25 or 50 IU/kg rIX-FP administration, the baseline-corrected mean FIX activity remained elevated at day 7 (7.4 IU/dL and 13.4 IU/dL, respectively) and day 14 (2.5 IU/dL and 5.5 IU/dL, respectively). The incremental recovery of rIX-FP was higher than both recombinant and plasma-derived FIX (1.4 vs 0.95 and 1.1 IU/dL per IU/kg, respectively). These results demonstrated both the safety and improved pharmacokinetics of rIX-FP, thus indicating this new product with extended half-life as possibly able to control and prevent bleeding with less frequent injection.

Garadacimab for hereditary angioedema attack prevention: long-term efficacy, quality of life, and safety data from a phase 2, randomised, open-label extension study.

BACKGROUND: Garadacimab is a fully human immunoglobulin G4 monoclonal antibody targeting activated factor XII. This study evaluated long-term efficacy, health-related quality of life (HRQoL), and safety data for garadacimab in adults with hereditary angioedema. METHODS: This global phase 2 study comprised a treatment period 1 (TP1: 12 weeks, double-blind, placebo-controlled) and a treatment period 2 (TP2: ≥44-week open-label extension). Patients aged 18-65 years with clinically confirmed hereditary angioedema were eligible. In TP1, 32 patients were randomly assigned (1:1:1:1) to receive subcutaneous garadacimab (75 mg, 200 mg, or 600 mg) or placebo every 4 weeks (once monthly). Randomisation was done using interactive response technology via block randomisation (block sizes 1-4). Subsequently, six additional patients in TP1 were assigned to open-label garadacimab 400 mg every 2 weeks. At the start of TP2, patients were re-randomised (if receiving placebo, garadacimab 75 mg, or garadacimab 400 mg) or continued to receive garadacimab 200 mg or garadacimab 600 mg once monthly. After a protocol amendment on March 20, 2020, patients originally assigned to the 600 mg dose were down-titrated to 200 mg at their next visit. The primary endpoint (published previously) was monthly attack rate for patients receiving 200 mg or 600 mg garadacimab in TP1 in the intention-to-treat population. Here, we assessed the impact of garadacimab on patient-reported and investigator-reported outcomes and HRQoL as well as long-term efficacy and safety. This trial is registered with ClinicalTrials.gov, NCT03712228, and is completed. FINDINGS: Of 54 patients screened between Oct 29, 2018, and Aug 28, 2019, 32 randomised and six open-label patients completed TP1 and entered TP2 (20 in the garadacimab 200 mg group; 18 in the garadacimab 600 mg group; total 38 patients). Median age was 39·0 years (IQR 27·0-53·0), and 21 patients (55%) were female and 17 (45%) were male. In TP2, the median garadacimab exposure was 87·9 weeks (IQR 50·0-106·6) in the garadacimab 200 mg group and 44·1 weeks (24·1-56·1) in the garadacimab 600 mg group. Median monthly attack rates were 0·0 (IQR 0·0-0·1) in the garadacimab 200 mg group and 0·1 (0·0-0·4) in the garadacimb 600 mg group. Median reduction in monthly attack rate versus run-in was 100% (IQR 98-100) with garadacimab 200 mg. HRQoL improvements observed during TP1 with garadacimab were sustained throughout TP2. TP2 safety signals were consistent with TP1. Two patients experienced serious adverse events of diverticular perforation and asthma (not garadacimab-related). Treatment-emergent adverse events were mostly mild or moderate in severity. The most common adverse events were headache (nine of 38, 24%) and abdominal pain (seven of 38, 18%). There were no treatment-related deaths. INTERPRETATION: Once-monthly garadacimab for more than 2 years in patients with hereditary angioedema was well tolerated and efficacious in reducing monthly attack rate and improving HRQoL. These results reveal the potential of long-term prophylactic treatment with 200 mg once-monthly garadacimab towards complete disease control of patients with hereditary angioedema. FUNDING: CSL Behring.

Long-Term Outcomes with Subcutaneous C1-Inhibitor Replacement Therapy for Prevention of Hereditary Angioedema Attacks.

BACKGROUND: For the prevention of attacks of hereditary angioedema (HAE), the efficacy and safety of subcutaneous human C1-esterase inhibitor (C1-INH[SC]; HAEGARDA, CSL Behring) was established in the 16-week Clinical Study for Optimal Management of Preventing Angioedema with Low-Volume Subcutaneous C1-Inhibitor Replacement Therapy (COMPACT). OBJECTIVE: To assess the long-term safety, occurrence of angioedema attacks, and use of rescue medication with C1-INH(SC). METHODS: Open-label, randomized, parallel-arm extension of COMPACT across 11 countries. Patients with frequent angioedema attacks, either study treatment-naive or who had completed COMPACT, were randomly assigned (1:1) to 40 IU/kg or 60 IU/kg C1-INH(SC) twice per week, with conditional uptitration to optimize prophylaxis (ClinicalTrials.gov registration no. NCT02316353). RESULTS: A total of 126 patients with a monthly attack rate of 4.3 in 3 months before entry in COMPACT were enrolled and treated for a mean of 1.5 years; 44 patients (34.9%) had more than 2 years of exposure. Mean steady-state C1-INH functional activity increased to 66.6% with 60 IU/kg. Incidence of adverse events was low and similar in both dose groups (11.3 and 8.5 events per patient-year for 40 IU/kg and 60 IU/kg, respectively). For 40 IU/kg and 60 IU/kg, median annualized attack rates were 1.3 and 1.0, respectively, and median rescue medication use was 0.2 and 0.0 times per year, respectively. Of 23 patients receiving 60 IU/kg for more than 2 years, 19 (83%) were attack-free during months 25 to 30 of treatment. CONCLUSIONS: In patients with frequent HAE attacks, long-term replacement therapy with C1-INH(SC) is safe and exhibits a substantial and sustained prophylactic effect, with the vast majority of patients becoming free from debilitating disease symptoms.

Long-acting recombinant fusion protein linking coagulation factor IX with albumin (rIX-FP) in children. Results of a phase 3 trial.

A global phase 3 study evaluated the pharmacokinetics, efficacy and safety of a recombinant fusion protein linking coagulation factor IX with albumin (rIX-FP) in 27 previously treated male children (1-11 years) with severe and moderately severe haemophilia B (factor IX [FIX] activity ≤2 IU/dl). All patients received routine prophylaxis once every seven days for up to 77 weeks, and treated any bleeding episodes on-demand. The mean terminal half-life of rIX-FP was 91.4 hours (h), 4.3-fold longer than previous FIX treatment and clearance was 1.11 ml/h/kg, 6.4-fold slower than previous FIX treatment. The median (Q1, Q3) annualised spontaneous bleeding rate was 0.00 (0.00, 0.91) and was similar between the <6 years and ≥6 years age groups, with a weekly median prophylactic dose of 46 IU/kg. In addition, patients maintained a median trough level of 13.4 IU/dl FIX activity on weekly prophylaxis. Overall, 97.2 % of bleeding episodes were successfully treated with one or two injections of rIX-FP (95 % CI: 92 % to 99 %), 88.7 % with one injection, and 96 % of the treatments were rated effective (excellent or good) by the Investigator. No patient developed FIX inhibitors and no safety concerns were identified. These results indicate that rIX-FP is safe and effective for preventing and treating bleeding episodes in children with haemophilia B with weekly prophylaxis. Routine prophylaxis with rIX-FP at treatment intervals of up to 14 days are currently being investigated in children with severe and moderately severe haemophilia B. Clinicaltrials.gov (NCT01662531).

Differential regulation of nicotinic receptor-mediated neurotransmitter release following chronic (-)-nicotine administration.

The objective of this study was to compare nAChR-mediated neurotransmitter release from slices of rat striatum, frontal cortex and hippocampus following chronic (-)-nicotine (Nic) administration (tartrate salt, 2 mg/kg twice daily for 10 days). Binding studies were also conducted to measure changes in receptor density. Relative to saline-treated animals, the number of nAChRs measured by [(3)H]-cytisine (CYT) binding was significantly increased in all brain regions examined by 15% to 25% following chronic Nic administration. Using a relatively high throughput method to measure neurotransmitter release, we found that Nic, CYT, and (+/-)-epibatidine (EB) evoked similar concentration-dependent striatal [(3)H]-dopamine (DA) and hippocampal [(3)H]-norepinephrine (NE) release from both saline (rank order of potency for [(3)H]-DA: EB>CYT>Nic; pEC(50) values, EB (9 +/- 0.1), CYT (8 +/- 0.13), Nic (7.3 +/- 0.19); rank order potency for [(3)H]-NE: EB>Nic=CYT; pEC(50) values, EB (8 +/- 0.18), Nic (5.5 +/- 0.09), CYT (5.12 +/- 0.1)) -and Nic-treated animals (pEC(50) values [(3)H]-DA, EB (9.5 +/- 0.15), Nic (8 +/- 0.16, CYT (6.6 +/- 0.52); [(3)H]-NE, EB (8.4 +/- 0.23), Nic (5.19 +/- 0.1), CYT (5.18 +/- 0.29)). Although no change in potency was detected between the two treatment groups, the agonist efficacies in both tissues were significantly reduced by approximately 17-54% following chronic Nic administration. In contrast to striatum, treatment with Nic did not affect the maximal [(3)H]-DA response (efficacy) in the frontal cortex. However, as observed in the striatum, no change in agonist potency was observed in the frontal cortex following chronic Nic administration (pEC(50) values, saline; EB (9.2 +/- 0.2), >CYT (6.95 +/- 0.75) = Nic (6.9 +/- 0.16); Nic-treated, EB (9 +/- 0.42)>CYT (6.88 +/- 0.27) = Nic (7.1 +/- 0.17)). Chronic Nic treatment did not significantly affect KCl-evoked [(3)H]-NE release from hippocampus or [(3)H]-DA release from frontal cortex or striatum. Since previous work has demonstrated that different nAChR subtypes display various sensitivities to chronic Nic exposure, we suggest that the subtypes of nAChRs involved in regulating [(3)H]-DA release may be different in the striatum and frontal cortex. These results support findings from earlier studies comparing the pharmacology of nAChR-evoked striatal versus cortical [(3)H]-DA release.