Sacituzumab govitecan, a Trop-2-directed antibody-drug conjugate, for patients with epithelial cancer: final safety and efficacy results from the phase I/II IMMU-132-01 basket trial

BACKGROUND

Sacituzumab govitecan (SG), a trophoblast cell surface antigen-2 (Trop-2)-directed antibody-drug conjugate, has demonstrated antitumor efficacy and acceptable tolerability in a phase I/II multicenter trial (NCT01631552) in patients with advanced epithelial cancers. This report summarizes the safety data from the overall safety population (OSP) and efficacy data, including additional disease cohorts not published previously.

PATIENTS AND METHODS

Patients with refractory metastatic epithelial cancers received intravenous SG (8, 10, 12, or 18 mg/kg) on days 1 and 8 of 21-day cycles until disease progression or unacceptable toxicity. Endpoints for the OSP included safety and pharmacokinetic parameters with investigator-evaluated objective response rate (ORR per RECIST 1.1), duration of response, clinical benefit rate, progression-free survival, and overall survival evaluated for cohorts (n > 10 patients) of small-cell lung, colorectal, esophageal, endometrial, pancreatic ductal adenocarcinoma, and castrate-resistant prostate cancer.

RESULTS

In the OSP (n = 495, median age 61 years, 68% female; UGT1A1∗28 homozygous, n = 46; 9.3%), 41 (8.3%) permanently discontinued treatment due to adverse events (AEs). Most common treatment-related AEs were nausea (62.6%), diarrhea (56.2%), fatigue (48.3%), alopecia (40.4%), and neutropenia (57.8%). Most common treatment-related serious AEs (n = 75; 15.2%) were febrile neutropenia (4.0%) and diarrhea (2.8%). Grade ≥3 neutropenia and febrile neutropenia occurred in 42.4% and 5.3% of patients, respectively. Neutropenia (all grades) was numerically more frequent in UGT1A1∗28 homozygotes (28/46; 60.9%) than heterozygotes (69/180; 38.3%) or UGT1A1∗1 wild type (59/177; 33.3%). There was one treatment-related death due to an AE of aspiration pneumonia. Partial responses were seen in endometrial cancer (4/18, 22.2% ORR) and small-cell lung cancer (11/62, 17.7% ORR), and one castrate-resistant prostate cancer patient had a complete response (n = 1/11; 9.1% ORR).

CONCLUSIONS

SG demonstrated a toxicity profile consistent with previous published reports. Efficacy was seen in several cancer cohorts, which validates Trop-2 as a broad target in solid tumors.

Sacituzumab govitecan in previously treated hormone receptor-positive/HER2-negative metastatic breast cancer: final results from a phase I/II, single-arm, basket trial

BACKGROUND

Trophoblast cell-surface antigen-2 (Trop-2) is expressed in epithelial cancers, including hormone receptor-positive (HR+) metastatic breast cancer (mBC). Sacituzumab govitecan (SG; Trodelvy®) is an antibody-drug conjugate composed of a humanized anti-Trop-2 monoclonal antibody coupled to SN-38 at a high drug-to-antibody ratio via a unique hydrolyzable linker that delivers SN-38 intracellularly and in the tumor microenvironment. SG was granted accelerated FDA approval for metastatic triple-negative BC treatment in April 2020.

PATIENTS AND METHODS

We analyzed a prespecified subpopulation of patients with HR+/human epidermal growth factor receptor 2-negative (HER2-) HR+/HER2- mBC from the phase I/II, single-arm trial (NCT01631552), who received intravenous SG (10 mg/kg) and whose disease progressed on endocrine-based therapy and at least one prior chemotherapy for mBC. End points included objective response rate (ORR; RECIST version 1.1) assessed locally, duration of response (DOR), clinical benefit rate, progression-free survival (PFS), overall survival (OS), and safety.

RESULTS

Fifty-four women were enrolled between 13 February 2015 and 1 June 2017. Median (range) age was 54 (33-79) years and all received at least two prior lines of therapy for mBC. At data cut-off (1 March 2019), 12 patients were still alive. Key grade ≥3 treatment-related toxicities included neutropenia (50.0%), anemia (11.1%), and diarrhea (7.4%). Two patients discontinued treatment due to treatment-related adverse events. No treatment-related deaths occurred. At a median follow-up of 11.5 months, the ORR was 31.5% [95% confidence interval (CI), 19.5%-45.6%; 17 partial responses]; median DOR was 8.7 months (95% CI 3.7-12.7), median PFS was 5.5 months (95% CI 3.6-7.6), and median OS was 12 months (95% CI 9.0-18.2).

CONCLUSIONS

SG shows encouraging activity in patients with pretreated HR+/HER2- mBC and a predictable, manageable safety profile. Further evaluation in a randomized phase III trial (TROPiCS-02) is ongoing (NCT03901339).

TRIAL REGISTRATION

ClinicalTrials.gov NCT01631552; https://clinicaltrials.gov/ct2/show/NCT01631552.

Abstract P2-11-01: Safety and efficacy of sacituzumab govitecan (anti-Trop-2-SN-38 antibody-drug conjugate) as ≥3rd-line therapeutic option for treatment-refractory HER2-negative metastatic breast cancer (HER2Neg mBC)

Background: Sacituzumab govitecan is an antibody-drug conjugate consisting of SN-38, the active metabolite of irinotecan, conjugated to a humanized mAb targeting Trop-2 (trophoblastic antigen-2), which is highly expressed in many epithelial cancers. A phase I/II basket trial (NCT01631552) investigated its activity in patients (pts) with advanced epithelial cancers. Herein, we summarize pooled safety and efficacy findings in 162 pts with HER2-negative metastatic breast cancer (mBC) accrued between 7/2013 and 6/2017 who received at least 2 prior therapies for metastatic disease and were treated with sacituzumab govitecan at the 10 mg/kg dose level.

Methods: Patients with triple-negative (N=108) and patients with hormone-receptor positive (N=54) mBC received 10 mg/kg sacituzumab govitecan on days 1 & 8 of a 21-day cycle continued until progression or unacceptable toxicity. All pts had measurable disease by CT or MRI. Efficacy was assessed locally by RECIST 1.1 including overall response rate (ORR) and Kaplan-Meier estimates of duration of response (DOR), progression-free survival (PFS) and overall survival (OS). Adverse events (AE) were evaluated according to CTCAE v4.0

Results: The patient cohort (161 female /1 male; median age 55 yrs, range 31-80) received a median of 4 prior therapies for metastatic disease (range 2-17), with prior chemotherapy agents in the metastatic setting including taxane (68%), capecitabine (60%), platinum (59%), gemcitabine (44%), eribulin (41%), and anthracycline (38%). 77 pts have died, with 57 in long-term follow-up and 28 still on treatment at data cutoff. The median number of administered sacituzumab govitecan doses was 14 (range 1-88). Treatment was generally well tolerated. 29% of pts had dose reductions, 3% discontinued treatment due to drug-related AEs, and there were no treatment-related deaths. Based on currently available AE data, grade ≥ 3 toxicity included neutropenia (43%), anemia (9.5%), diarrhea (7.0%) and febrile neutropenia (6.3%). For the TNBC subgroup, with a median follow-up of 9.3 months, the ORR was 33% (3 CRs + 33 PRs /108) with a median DOR of 8.3 months (95% CI: 4.8 – 11.6). For the ER+ subgroup, with a median follow-up of 10.0 months, the ORR was 31% (17 PRs/54) with a median DOR of 7.4 months (95% CI: 4.4 – 18.3). The combined HER2Neg ORR was 33% (3 CRs+50 PRs/162), with a median DOR of 8.3 months (95% CI: 4.9 - 10.8), PFS of 5.6 months (95% CI: 5.1 – 6.9) and OS of 13.0 months (95% CI: 11.5 - 15.0). The ORR was comparable for pts ≤ 50 yrs. old [32.2% (19/59)] vs. > 50 yrs old [33.0% (34/103)] and little different for pts with 2 prior therapies [35.4% (17/48)] vs. >2 prior therapies [31.6% (36/114)].

Conclusions: Monotherapy with sacituzumab govitecan was well tolerated with a manageable safety profile, and achieved a 30+% objective response rate among heavily pre-treated patients with HER2-negative metastatic breast cancer regardless of ER status.

Citation Format: Kalinsky K, Isakoff SJ, Tolaney SM, Juric D, Mayer IA, Vahdat LT, Diamond JR, O'Shaughnessy J, Moroose RL, Santin AD, Shah NC, Abramson V, Goldenberg DM, Sharkey RM, Washkowitz SA, Wegener WA, Iannone R, Bardia A. Safety and efficacy of sacituzumab govitecan (anti-Trop-2-SN-38 antibody-drug conjugate) as ≥3rd-line therapeutic option for treatment-refractory HER2-negative metastatic breast cancer (HER2Neg mBC) [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 P2-11-01.

Abstract OT2-07-05: A phase III, randomized trial of sacituzumab govitecan (IMMU-132) vs treatment of physician choice (TPC) for metastatic triple-negative breast cancer (mTNBC)

Background: Metastatic TNBC has an aggressive course with limited therapy options and poor survival. Sacituzumab govitecan (IMMU-132) is a novel antibody drug conjugate consisting of SN-38, the active metabolite of the topoisomerase I inhibitor, irinotecan, conjugated to a humanized mAb targeting Trop-2, which is highly expressed in most epithelial cancers, including TNBC. We previously reported that patients (pts) with mTNBC treated with IMMU-132 after a median of 5 prior therapies from initial diagnosis achieved a 30% objective response rate (ORR), 8.9 mo median duration of response (DOR), and an acceptable safety profile with nausea, neutropenia, and diarrhea the most common toxicities (Bardia et al., JCO, 2017). IMMU-132 was awarded Breakthrough Designation by the FDA based on this data. Accordingly, we are enrolling additional patients with relapsed/refractory mTNBC with intention of seeking regulatory approval as a ≥3rd-line therapeutic option.

Trial design: An international, open-label, Phase III study in pts with refractory/relapsed mTNBC after ≥2 prior chemotherapies for advanced disease or >1 therapy for pts who progress within 12 months of adjuvant therapy (NCT02574455). Pts are randomized 1:1 to receive either IMMU-132 (10 mg/kg IV, days 1 and 8 every 21 days) or TPC from one of 4 prespecified single-agent regimens (capecitabine, eribulin, vinorelbine or gemcitabine). Pts continue treatment until progression requiring discontinuation or unacceptable toxicity. The primary endpoint is progression-free survival (PFS) and additional endpoints include overall survival (OS), ORR, DOR, safety and quality of life. Independent, blinded reads of scans will be performed.

Eligibility criteria: Adults >18 yrs old, with metastatic breast cancer, triple-negative by most recent biopsy, measurable disease by CT or MRI as per RECIST1.1, ECOG performance score 0 or 1, adequate safety laboratories. Refractory/relapsed after ≥2 prior standard chemotherapy regimens for advanced disease, or >1 therapy for pts who progress within 12 months of adjuvant therapy. Pts must have received taxane and be eligible by investigator to receive at least one of the TPC agents. Pts with treated, non-progressive brain metastases are eligible.

Specific aims: To compare IMMU-132 to TPC as measured by PFS, OS, ORR, DOR,QOL, adverse events, safety laboratories, incidence of dose delays and reductions, and treatment discontinuations due to toxicity.

Statistical methods: Assuming a median PFS of 3 mo. and OS of 10 mo. with TPC vs. 5 and 15 mo. with IMMU-132, respectively, a study size of 328 patients has >95% and >80% power to detect a statistically significant difference in PFS and OS, respectively, between the two treatment arms.

Present accrual and target accrual: Trial enrollment will begin prior to SABCS 2017 with approximately 328 patients expected to be enrolled over 18 months at approximately 100 institutions in North America, Europe and potentially elsewhere.

Contact: Immu132@Immunomedics.com

Citation Format: Bardia A, Rugo HS, Horne H, Wegener WA, Goldenberg DM, O'Shaughnessy J. A phase III, randomized trial of sacituzumab govitecan (IMMU-132) vs treatment of physician choice (TPC) for metastatic triple-negative breast cancer (mTNBC) [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr OT2-07-05.

Abstract P1-12-01: Withdrawn

This abstract was withdrawn by the authors.

Abstract P4-22-15: Sacituzumab govitecan (IMMU-132), an anti-Trop-2-SN-38 antibody-drug conjugate (ADC) for the treatment of relapsed/refractory, metastatic triple-negative breast cancer (mTNBC): Updated results

Background. mTNBC has an aggressive course with limited effective therapy options and a median progression-free survival (PFS) of 2-4 months (mos) with standard therapy. Sacituzumab govitecan (IMMU-132) is an ADC targeting Trop-2, an antigen present in many epithelial cancers, including TNBC, and delivering SN-38, a topoisomerase I inhibitor as its therapeutic moiety. IMMU-132 was awarded Breakthrough Therapy designation by FDA based on its previously reported activity in relapsed/refractory mTNBC patients. Here we present updated results from the mTNBC cohort of an ongoing phase I/II study (ClinicalTrials.gov, NCT01631552).

Methods. mTNBC patients (pts) received IMMU-132 10 mg/kg on days 1 and 8 every 21 days. Trop-2 expression was not required for enrollment, but available tumor specimens underwent immunohistological (IHC) testing. Efficacy was assessed locally by RECIST 1.1; ORR, PFS and overall survival (OS) were determined for all pts. Pharmacokinetic parameters were estimated in select pts with adequate blood sampling. Immunogenicity to IMMU-132 was examined in all pts.

Results. We previously reported preliminary efficacy results in 51 mTNBC patients. Here we present data on 69 patients with data cutoff June 5, 2016. Median age was 56 years (31-81) and a median of 5 prior therapies (range 1-12), with 66 evaluable for response; ORR was 29% (19/66) 2 confirmed complete (CR) and 17 confirmed partial responses (PR). The median intention-to-treat PFS is 5.6 mos (95% CI, 3.6-7.1 mos) and median OS is 14.3 mos (95% CI, 10.5-18.8 mos). PRs included 2 pts whose tumors did not respond to anti-PD-L1 therapy. The duration of response in the 19 confirmed responders (8 continuing therapy) is 11.5 mos (95% CI = 7.6 to 12.7). The clinical benefit rate (CR+PR+SD>6 mos) for the 66 assessable patients is currently 45.5%. The majority (88%) of archival tumor specimens were moderately (2+) to strongly (3+) positive by IHC for Trop-2, precluding using Trop-2 expression as a selection criterion. Among current adverse events, grade >3 drug-related toxicities included neutropenia (35%), leukopenia (16%), anemia (13%), vomiting (9%), diarrhea (10%), and febrile neutropenia (4%). Clearance kinetics in 8 pts showed IMMU-132 and IgG had a terminal half-life of 15.3 ± 2.7 h and 86.5 ± 40.5 h, respectively, with area under the curve for free SN-38 (unbound) only 3% of the total amount of SN-38 (e.g., IgG bound). Thus, most SN-38 remains bound to the conjugate, and is released at a rate predicted from in vitro serum stability studies. No pt developed anti-IMMU-132 antibodies.

Conclusion The Trop-2-targeting ADC, IMMU-132, delivering cytotoxic doses of SN-38, shows high objective and durable tumor responses with manageable toxicity in heavily-pretreated pts with mTNBC in this updated cohort, supporting further development in this population with an unmet medical need.

Citation Format: Bardia A, Diamond JR, Mayer IA, Isakoff SJ, Abramson V, Starodub AN, O'Shaughnessy J, Kalinsky K, Moroose R, Shah N, Juric D, Shapiro GI, Guarino M, Ocean AJ, Messersmith WA, Berlin JD, Wegener WA, Sharkey RM, Goldenberg DM, Vahdat LT. Sacituzumab govitecan (IMMU-132), an anti-Trop-2-SN-38 antibody-drug conjugate (ADC) for the treatment of relapsed/refractory, metastatic triple-negative breast cancer (mTNBC): Updated results [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 P4-22-15.

Abstract PD3-06: Safety and efficacy of anti-Trop-2 antibody drug conjugate, sacituzumab govitecan (IMMU-132), in heavily pretreated patients with TNBC

Background: Triple-negative breast cancer (TNBC) comprises about 15% of all breast cancer types, and has a particularly aggressive course. Following first-line therapy, the median PFS is <3 months, and OS is <10 months. Therefore, new treatment strategies are needed. Since Trop-2 is expressed in >90% of TNBC, as measured by IHC, we conducted a trial to evaluate the safety and efficacy of a humanized anti-Trop-2 monoclonal antibody conjugated to a high concentration of SN-38, a camptothecin that is a topoisomerase I inhibitor and the active metabolite of the prodrug irinotecan, with 2-3 logs higher potency than the prodrug.

Methods: After establishing the optimal repeated dose in a Phase I trial (ClinicalTrials.gov, NCT01631552) involving many different solid cancer types, an expanded Phase II was undertaken in a number of cancers, including TNBC. Patients received 8 or 10 mg/kg IMMU-132 i.v. on days 1 and 8 of 21-day repeated cycles. Assessments of safety and response by RECIST1.1 were made weekly and bimonthly, respectively. Tumor biopsies (archival, at baseline prior to treatment, and at disease progression) were obtained when safe and feasible.

Results: As of May 10, 2015, 58 patients with TNBC, with a median of 4 prior therapies (range, 1-11), were treated with IMMU-132. Grade 3-4 toxicities included neutropenia (26%), febrile neutropenia (2%), diarrhea (2%), anemia (4%), and fatigue (4%). No patient developed antibodies to SN-38 or the antibody, and no patient discontinued therapy due to toxicity. Tumor responses were defined as ORR (CR+PR) in 31% of 49 evaluated patients, including 2 with CR, and a clinical benefit ratio (CR+PR+SD>6 mo) of 49% (63% with SD>4 mo; 23 patients continuing treatment after 1st assessment). The current median progression-free survival is 7.3 months with 44% maturity in 50 patients treated at the 8 or 10 mg/kg dose level. Overall survival data are still not mature 20 months after enrollment of first patient. Clinical efficacy correlated to biomarker studies, including Trop-2 expression (target of antibody), topoisomerase-1 expression (target of SN-38), and homologous recombinant deficiency (HRD) assay (marker of DNA repair), is being studied. Immunohistochemistry results in archival specimens currently show 97% positivity of Trop-2 among 34 specimens evaluated, with 79% having high intensity (2+/3+) staining.

Conclusions: The Trop-2-targeting IMMU-132, delivering cytotoxic doses of the topoisomerase I inhibitor, SN-38, shows manageable toxicity, and encouraging anti-tumor activity in relapsed/refractory patients with TNBC. This ADC appears to have a high therapeutic index in heavily pretreated patients.

Citation Format: Bardia A, Diamond JR, Mayer IA, Starodub AN, Moroose RL, Isakoff SJ, Ocean AJ, Guarino MJ, Berlin JD, Messersmith WA, Thomas SS, O'Shaughnessy JA, Kalinsky K, Maurer M, Chang JC, Forero A, Traina T, Gucalp A, Wilhelm F, Wegener WA, Maliakal P, Sharkey RM, Goldenberg DM, Vahdat LT. Safety and efficacy of anti-Trop-2 antibody drug conjugate, sacituzumab govitecan (IMMU-132), in heavily pretreated patients with TNBC. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr PD3-06.

Activity of fractionated radioimmunotherapy with clivatuzumab tetraxetan combined with low-dose gemcitabine (Gem) in advanced pancreatic cancer (APC)

240

Background: The90Y-labeled anti-mucin humanized mAb, clivatuzumab tetraxetan (90Y-hPAM4), is in clinical development in APC. A phase I/II trial of 90Y-hPAM4 with low-dose radiosensitizing Gem has now concluded 90Y-dose escalation.

Methods: Pts with untreated, inoperable, stage 3-4 APC received 200 mg/m2 Gem once-weekly x 4 with 90Y-hPAM4 on wks 2-4, and with 90Y escalated in cohorts by 3+3 design. Tumor responses were assessed by CT, FDG/PET and serum CA19.9, with cycles repeated until progression or unacceptable toxicity.

Results: Of 42 pts (40-87 yrs, ECOG PS 0-1, 36 stage 4), 4 withdrew early while 38 received weekly x 3 90Y doses of 6.5 (N=4), 9 (N=12), 12 (N=17) and 15 (N=5) mCi/m2. Treatment was well-tolerated with few non-hematologic side-effects, including 13 pts retreated with 1-3 additional cycles. CTCv3 grade 3-4 plts or ANC developed in 21/38 (55%) pts after cycle 1 and all (100%) retreated pts after last cycle. Escalation reached limits on radiation doses to the marrow, but hematologic suppression was reversible without major infections or bleeding events, except for 3 pts after repeated cycles, one with extensive marrow tumor infiltration. By CT, the overall disease control rate was 55%, including 6 pts (16%) with partial responses (PRs) by RECIST criteria and 15 pts (39%) with stabilization as best response. After cycle 1, 43% (10/23) improved by PET studies (negative or >25% reduced uptake), and 36% (9/25) with elevated CA19.9 levels had >50 decreases. With 26% (10/38) of pts still in follow-up, 55% (21/38) have now achieved survival of ≥ 6 months [18% (7/38) ≥ 1 yr]. Treatment outcome may increase with 90Y dose, since pts treated at 3 x ≥12 mCi/m2 vs ≤9 mCi/m2 had 19% vs 6% PRs by CT, 47% vs 22% CA19.9 decreases, 63% vs 25% PET improvement, and 64% vs. 44% survival ≥ 6 months. Anecdotally, PS and pain level improved, which needs validation. Updated survival will be presented at the meeting.

Conclusions: Fractionated 90Y-hPAM4 plus low-dose Gem showed encouraging therapeutic activity with manageable hematological toxicity. The 12-mCi/m2 dose level was selected for continued dose exploration now underway, involving standard Gem doses and adding maintenance Gem.

[Table: see text]

A general ellipsoid cannot always serve as a model for the rotational diffusion properties of arbitrarily shaped rigid molecules

An ellipsoidally shaped body, or more commonly, an ellipsoid of revolution, is generally assumed to serve as a convenient model for evaluating the rotational diffusion properties of macromolecules. If Perrin's equations for the rotational diffusion coefficients of general ellipsoids can be shown to generate all possible rotational diffusion coefficients, then there would exist at least one equivalent ellipsoidal shape for every arbitrarily shaped rigid body. We investigated the problem by first generating a space, r-space, representing all possible ellipsoidal shapes. We then generated another space, D-space, representing all possible combinations of rotational diffusion coefficients. We then mapped r-space into D-space by using Perrin's equations. Ellipsoidal shapes map into diffusion space in a well-defined manner. The mapping is either 1:1, 2:1, or 3:1; several distinctly different regions of r-space map onto the same regions of D-space. Thus, for some combinations of rotational diffusion coefficients, more than one ellipsoid can be used as a model. Not all of D-space is covered by the mapping of r-space. Therefore, there are combinations of rotational diffusion coefficients that cannot be generated from ellipsoidally shaped bodies. Several examples of rigid body shapes with nonellipsoidal diffusion properties are described.

Dose-escalation trial of milatuzumab (humanized anti-CD74 monoclonal antibody) in multiple myeloma

8593

Background: CD74 (HLA-DR-associated invariant chain) is highly expressed in multiple myeloma (MM), rapidly internalized, and a promising target for immunotherapy. Methods: A multicenter dose-escalation study was initiated in patients (pts) with relapsed/refractory MM who had failed at least 2 standard therapies. Pts received milatuzumab IV twice-weekly for 4 wks, with doses escalated by a 3+3 cohort design. Pts were evaluated over 12 wks, with responding pts continuing follow-up. AEs and safety laboratories were evaluated by NCI CTC v3 grades, with any treatment-related Grade 3–4 events considered dose-limiting toxicity (DLT). Responses were classified by EBMT criteria, with PK and immunogenicity evaluated by serum milatuzumab levels and human anti-milatuzumab antibody (HAHA) titers, respectively. Results: Twenty-one pts (12M/9F, median age 63) have now received 1.5 (n=8), 4.0 (n=9) or 8.0 mg/kg (n=4) doses twice weekly. They had MM for 0.9–16.8 years (median 5.4), predominantly IgG subtype, were heavily pretreated (4 median prior treatments), and were Durie-Salmon stage II (n=13) or III (n=8). After increasing premedications and slowing administration, infusions were well tolerated (Grade 1–2). There was 1 DLT (infusion reaction) and 3 SAEs (bact. meningitis, confusion/hypercalcemia, fever post demerol) at 1.5 mg/kg, 1 DLT (unexplained anemia) and 2 SAEs (cord compression, epistaxis/thrombocytopenia), at 4.0 mg/kg, but no DLTs or SAEs at 8.0 mg/kg. There has been no pattern of other AEs nor effects on routine laboratories, including serum chemistries, CBC, serum immunoglobulins, B- or T-cells, and no cases of HAHA. At current doses, milatuzumab is rapidly cleared from serum, with little accumulation and low trough levels across infusions. There have been no objective responses so far, but 4 pts have had stable disease by EBMT criteria for at least 3 months post-treatment, occurring with a possible trend towards higher milatuzumab serum levels than pts with earlier disease progression. Conclusions: Milatuzumab doses up to 8.0 mg/kg may be given safely twice-weekly for 4 weeks. In spite of rapid clearance, several patients have had disease stabilization at 4.0 and 8.0 mg/kg doses, which is encouraging. Accrual of the next cohort receiving 16.0 mg/kg is ongoing.

[Table: see text]

Multicenter study of radiosensitizing gemcitabine combined with fractionated radioimmunotherapy for repeated treatment cycles in advanced pancreatic cancer

4620

Background: In a phase I study, a single dose of 90Y-labeled anti-mucin humanized antibody, hPAM4 (90Y-hPAM4), led to several transient reductions or stabilization of lesions in advanced pancreatic cancer, with bone marrow toxicity limiting the maximum tolerated dose to 20 mCi/m2. Preclinical studies showed gemcitabine enhanced radioimmunotherapy, so a phase Ib study was undertaken to evaluate repeated treatment cycles of 90Y-hPAM4 plus gemcitabine. Methods: Patients (pts) with previously untreated, locally advanced or metastatic, pancreatic cancer were treated in 4-week cycles (200 mg/m2 gemcitabine once-weekly; 111In-hPAM4 the 1st wk for imaging, biodistribution, and dosimetry; 90Y-hPAM4 once-weekly the last 3 wks), which could be repeated in the absence of progression or unacceptable toxicity. The 90Y-dose was escalated by patient cohort following a 3+3 design, with tumor responses assessed by CT and FDG/PET imaging, and by CA19.9 serum levels. Results: Eight pts (3F/5M, 56–72 years old, 7 with metastatic disease) have now been treated at the first 2 dose levels (6.5 and 9.0 mCi/m2 90Y-hPAM4 x 3) with hematologic toxicity all transient Grade 1–2 (NCI CTC v3). 111In-hPAM4 imaging showed normal biodistribution, evidence of tumor targeting and acceptable dosimetry estimates to normal organs per treatment cycle. Two pts had tumor responses to initial treatment with significant decreases in FDG metabolic activity on PET imaging, regression of lesion sizes on CT, and CA19.9 decreases. Both pts continue in excellent performance status now at 9 and 11 months after study entry, after receiving a total of 3 and 4 treatment cycles, respectively, without additional toxicity. A 3rd pt with a stable response by PET and CT 4 weeks after initial treatment and decreases in CA19.9 levels is now undergoing a 2nd treatment cycle. Four other pts had early progression of disease by or before post-treatment week-4 evaluation, and the remaining pt is still being evaluated. Conclusions: Dose escalation is continuing after fractionated radioimmunotherapy with 90Y-hPAM4 plus low-dose gemcitabine demonstrated therapeutic activity at the first two 90Y dose levels, with minimal hematologic toxicity, even after 4 treatment cycles.

[Table: see text]

Subcutaneous injections of low doses of veltuzumab (humanized anti-CD20 antibody): Objective responses in B-cell malignancies

8530

Background: Low IV doses of veltuzumab, a second-generation anti-CD20 monoclonal antibody with structure-function differences from chimeric rituximab, have shown clinical activity, thus justifying subcutaneous (SC) injections. Methods: A phase I/II study was initiated in patients (pts) with previously untreated or relapsed CD20+ indolent NHL or CLL who received 4 SC injections of veltuzumab 2 weeks apart at dose levels of 80, 160, or 320 mg. Efficacy was assessed by CT-based IWG (NHL) or hematology-based NCI/IWCLL (CLL) criteria 4 and 12 weeks later, with responding pts continuing follow-up. Other evaluations included AEs, safety laboratories, B-cell blood levels (CD19), serum veltuzumab levels, and human anti-veltuzumab antibody (HAHA) titers. Results: Nineteen pts (8M/11F, median age 63), including 14 NHL pts (11 follicular, 3 other indolent NHL; 5 treatment naive) most with stage III or IV disease (11/14) and 5 CLL pts (4 treatment naïve) all with Rai stage II or III disease, have now received SC veltuzumab at 80 mg (3 NHL, 3 CLL), 160 mg (9 NHL, 2 CLL) or 320 mg (2 NHL) dose levels. Pre-treatment with antihistamines or steroids has not been required, and SC veltuzumab was well tolerated with only mild, transient injection site reactions and tenderness. To date, all HAHA results have been negative. In NHL pts, SC veltuzumab demonstrates good bio-availability, with a slow release pattern over several days and depletion of circulating B cells starting after 1st injection. Initial response information is currently available for 10 pts. For 7 NHL pts, 4 weeks after treatment with 80 or 160 mg doses, 2 pts had partial responses, 3 pts showed stable disease, and 2 pts had disease progression. For 3 CLL pts who received 80 mg doses, serum veltuzumab levels were lower, but all pts still achieved 65–75% decreases in circulating leukemic cells over the course of treatment. Conclusions: SC administration of veltuzumab is well tolerated, achieves slow but efficient delivery into the blood, and is pharmacologically active. The low doses currently evaluated in B-cell malignancies show evidence of therapeutic activity, achieving objective responses in NHL and notable reductions in circulating leukemic cells in CLL.

[Table: see text]

First clinical experience with 90Y-radiolabeled humanized anti-MUC1 antibody (hPAM4) in patients with advanced pancreatic cancer: A phase I study

15034

Background: The humanized antibody, hPAM4, specifically targets an epitope in the mucin glycoprotein MUC1 expressed in most pancreatic cancers, but not normal pancreas or most other normal tissues. This study evaluated the dose-limiting toxicity (DLT), maximum tolerated dose (MTD), pharmacokinetics (PK), dosimetry and preliminary efficacy of 90Y-DOTA-hPAM4 administered as a single dose to patients (pts) with pancreatic adenocarcinoma. Methods: Pts with locally advanced disease and progression on 1 prior therapy (TX) or metastatic disease with 0–1 prior TX’s were eligible if they were ≥ 4 wks beyond prior TX, had adequate hematology/chemistries, with measurable disease, but no lesion >10 cm. Pts initially received 111In-hPAM4 followed by 7 days of serum samples and imaging for PK, biodistribution and organ radiation dose analysis. Pts then received a single infusion of 90Y-hPAM4 with the 90Y dose escalated in cohorts of 3–6 pts (5-mCi/m2 increments) until 2 evaluable pts/cohort encountered DLT. Treatment toxicity was evaluated by NCI CTC v. 3 criteria and tumor response by CT-based RECIST criteria. Results: Fifteen pts (8F/7M; median age 60; 11 metastatic/4 locally advanced;13 with, 2 without prior TX) received 90Y-hPAM4 at a dose level of 15 mCi/m2 (n=4), 20 mCi/m2 (n=7), and 25 mCi/m2 (n=4). Pre-therapy 111In-hPAM imaging showed acceptable biodistribution and organ radiation dosimetry in all pts. Four wks after treatment, 1 pt at 15 mCi/m2 and 2 pts at 20 mCi/m2 had CT responses, with 32–51% shrinkage of their pancreatic mass, while 3 other pts at various dose levels had stable target lesions by CT. All pts showed disease progression at or after wk 8. The only significant drug-related toxicity was hematologic, with >1 DLT (>7 day grade 4 thrombocytopenia and/or neutropenia) encountered at the 25 mCi/m2 level. Conclusions: For 90Y-hPAM administered once as a single agent, hematologic toxicity was dose-limiting, the MTD was established at 20 mCi/m2, and CT demonstrated several transient reductions or stabilization of index lesions. Based on this Phase I experience, combined/sequential treatment with chemotherapy and fractionated radioimmunotherapy is being considered for future trials.

No significant financial relationships to disclose.

Safety and efficacy of repeated anti-CEA radioimmunotherapy (RAIT) with 131I-labetuzumab post salvage resection of colorectal liver metastases

14507

Background: As shown recently (JCO 2005; 23:6763–70), a single application of RAIT improved both, median overall survival (OS), and 5-year survival rates of colorectal cancer (CRC) patients (pts) post salvage resection of liver metastases (LM) compared to controls without RAIT (P=0.004). In an ongoing phase II trial we are evaluating the safety and efficacy of repeated RAIT at doses of 2x 40–50 mCi/m2 (3 mos apart) post salvage resection of LM. Methods: To date, 26 pts (8x f, 18x m; age: 63 ± 9 ys) who underwent surgery for CRC-LM have received the first dose of 131I-labetuzumab (Immunomedics, In., NJ, USA), a humanized monoclonal antibody against CEA, within 2 months of LM surgery. Three months after the first RAIT, a second infusion of 40–50 mCi/m2 has been applied to all pts after completion of standardized re-staging procedures. Results: The primary tumor sites were 17 colonic and 9 rectal cancers; primary tumor stages were 5x UICC-II, 7x UICC-III, 14x UICC-IV. 13 pts received adjuvant therapy. In 11 pts preoperative chemotherapy (FOLFOX or FOLFIRI) was given to achieve resectability of bilobular LM. After resection of LM (y)mTNM tumor stages were 1x mTNM-I, 6x mTNM-II, 6x mTNM-III and 4x mTNM-IV, respectively. After first RAIT, hematologic Grade 3 and 4, toxicity (WBC/platelet count) occurred in 8/14 and 5/3 pts, respectively. No cumulative toxicity was seen after repeated RAIT, with complete bone marrow recovery observed in all cases so far. To date, all pts are alive. Of the total, 17 pts received RAIT with adjuvant intention (as classified by FDG-PET and CT scans at pre-RAIT re-staging). In these, DFS was 70% post salvage resection of LM during ongoing follow-up of 15 months (median; range: 4–23 mos). As of Dec. 20, 2006, cancer recurrence was detected in 5/17 pts (3x pulmonary, 1x intrahepatic, 1x both) and in 4 pts R0-resection of distant metastases was done. 1 patient with pulmonary and intrahepatic relapses receives polychemotherapy with palliative intention. The pts‘ compliance to repeated RAIT has been 100%. Conclusion: RAIT re-treatment to date appears to be safe, feasible, and well accepted. Extended follow-up of the encouraging survival data will be presented.

No significant financial relationships to disclose.

Chemoimmunotherapy reinduction with epratuzumab in children with ALL with marrow relapse: A Children's Oncology Group (COG) pilot study (ADVL04P2)

9513

Background: CD22, a 135kd protein restricted to B-cells, is expressed in > 90% of childhood B-precursor acute lymphoblastic leukemia (ALL). We conducted a feasibility/phase 2 study of epratuzumab, a humanized monoclonal antibody against CD22, with reinduction chemotherapy in children with relapsed CD22+ ALL. Methods: The feasibility portion (n=12) of the study is reported here. Patients with first or later ALL marrow relapse at any time following diagnosis, ± extramedullary disease, with = 25% blasts expressing CD22 and a presenting white blood cell count (WBC) of = 50,000/μl, were eligible. Therapy consisted of a 14-day single agent phase (epratuzumab 360 mg/m2 /dose IV twice weekly × 4 doses), followed by 4 weekly doses of epratuzumab in combination with standard reinduction chemotherapy (vincristine, prednisone, PEG-asparaginase, doxorubicin). Remission induction rates and minimal residual disease (MRD) by flow cytometry were determined at the end of this 6-week period. PK studies were performed by ELISA based immunoassay (prior + 30 minutes after infusions). Results: 12 evaluable patients, median age 10 years (range 3 - 18), were accrued. 9 pts were in 1st (n=5 early; n=4 late), and 3 pts in 2nd or later marrow relapse. The mean (±SD) trough epratuzumab concentration increased from 69±23 to 232±74 μg/ml during the initial 14 days. Surface CD22 was not detected by flow cytometry on peripheral blood leukemic blasts within 24 hours of drug administration in all but one patient, indicating effective targeting of leukemic cells by epratuzumab. The most frequent toxicities were grade 1–2 infusion reactions (n=9). Two dose limiting toxicities occurred: one patient had a Grade 4 seizure of unclear etiology and one patient had asymptomatic Grade 3 ALT elevation. 9 patients achieved a complete remission following chemoimmunotherapy, of whom 7 were MRD-negative. Conclusions: Treatment with epratuzumab plus standard reinduction chemotherapy is feasible and well tolerated in children with relapsed ALL, producing favorable early responses in the majority of patients. The phase II portion of the study is ongoing.

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Low doses of humanized anti-CD20 antibody, IMMU-106 (hA20), in refractory or recurrent NHL: Phase I/II results

8032

Background: An open-label, multicenter study has shown that the humanized anti-CD20 antibody, IMMU-106 (hA20), which has framework regions of epratuzumab, has a good safety and efficacy profile in NHL pts when administered once-weekly × 4 at different doses. The trial is now focused on confirming the efficacy of lower doses (80–120 mg/m2/wk × 4). Methods: A total of 68 pts (35 male, 33 female; age 34–84) received hA20 at 750 (N=3), 375 (N=27), 200 (N=11), 120 (N=21), or 80 mg/m2 (N=6). They had follicular (FL, N=47) or other (N=21) B-cell NHL, were predominantly stage III/IV (N=47) at study entry, and had received 1–8 prior treatments (median, 2), including 1 (N=40) or more (N=21) rituximab regimens (without progression within 6 months). Results: Sixty- six pts completed all 4 infusions; 1 pt progressed during treatment and withdrew, while another pt with hives and chills after prior rituximab discontinued treatment after a similar episode at 1st infusion. hA20 was generally well tolerated, with shorter infusion times (typically 2 h initially and 1 h subsequently) at lower doses. Drug-related adverse events were transient, Grade 1–2, most occurring only at 1st infusion, and there was no evidence of HAHA in 54 pts now evaluated. Mean antibody serum levels increased with dose and infusions; serum clearance at 375 mg/m2 appears similar to rituximab. Currently, 48 pts with at least 12 wks follow-up were evaluated by Cheson criteria: 32 FL pts had 15 (47%) OR's with 7 (22%) CR/CRu's, even after 2–4 prior rituximab-regimens, and 17 non-FL pts had 6 (38%) OR's, with 1 CRu in a marginal zone NHL pt. At a median follow-up of 11 mo., 9/21 pts with ORs are continuing responses, including 4 long-lived responses (15–20 mo). The evaluated pts include 17 pts at 120 mg/m2 who had 5 (29%) ORs with 3 (17%) CR/CRu's. Responses at 80 mg/m2 remain to be evaluated, but B-cell depletion occurs after the 1st infusion even at this low dose. Conclusions: hA20 appears well-tolerated, with no evidence of significant adverse events other than minor infusion reactions, even at short infusion times. B-cell depletion and responses have occurred at all doses evaluated, with no clear-cut evidence of a dose-response. As such, the study is continuing to confirm the efficacy of lower doses.

No significant financial relationships to disclose.

Phase I/II results of a second-generation humanized anti-CD20 antibody, IMMU-106 (hA20), in NHL

7530

Background: The humanized anti-CD20 antibody, IMMU-106 (hA20), has similar murine CDRs to rituximab, but the remaining framework is identical to humanized anti-CD22 IgG1 antibody, epratuzumab, whose safety and short infusion times have been reported. Methods: An open-label, multicenter, phase I/II, dose escalation study was conducted in adult patients with recurrent NHL to establish the safety, tolerance, PK, and immunogenicity (HAHA) of hA20 administered weekly x 4. Thirty-four patients have now received hA20 at 120 (n = 7), 200 (n = 6), 375 (n = 18) or 750 mg/m2 (n = 3). These were predominantly stage III/IV patients (n = 27) with follicular lymphoma (N = 23) who received 1–7 prior treatments (median, 2), including 1 (N = 22) or more (N = 9) rituximab regimens (without progression within 6 months). Results: Thirty-three patients completed all 4 hA20 infusions. Median infusion times at 375 mg/m2 were 3.1 h for 1st infusion, 2.0–2.3 h for subsequent infusions, and were generally shorter at lower doses. Fourteen patients (14%) had transient events, predominantly grade 1–2 events at 1st infusion. Antibody levels increased with hA20 dose; at 375 mg/m2, mean serum half-lives after 1st and 4th infusions were 3.4 ± 1.7 and 12.3 ± 3.9 days, respectively. With median follow-up now 3–6 months, peripheral blood B-cell depletion persists, HAHA evaluations are negative, and 14/23 patients (61%) with response assessments have objective responses by Cheson criteria. All 6 CR/CRu’s (23%) were in follicular lymphoma, occurred at all dose levels even at 120 mg/m2 (including patients with 2–4 prior rituximab-containing regimens ), and with 5/6 continuing. Conclusions: The tolerability, relatively short infusion times, and CR/CRu’s in patients with follicular lymphoma who relapsed after rituximab-containing regimens is encouraging. This study is continuing to assess response durability and to determine the optimal hA20 dose for subsequent studies.

[Table: see text]

Carcinoembryonic antigen immunoscintigraphy complements mammography in the diagnosis of breast carcinoma

BACKGROUND

An adjunctive noninvasive test that is predictable and highly specific for breast carcinoma would complement the high false-positive rate of mammography in certain patients.

METHODS

This prospective, multicenter study evaluated the accuracy, safety, and immunogenicity of carcinoembryonic antigen (CEA) antibody imaging in women with known or suspected breast carcinoma. Scintigraphic breast images were obtained approximately 3-8 hours after the administration of technetium 99m ((99)Tc) labeled anti-CEA Fab' and correlated with histopathology.

RESULTS

The (99)Tc labeled anti-CEA Fab' detected tumor CEA expression in 46 of 49 women (94%) initially entered with known primary breast carcinoma regardless of histology or serum CEA levels. In women scheduled for biopsy confirmation of mammographic and physical examination findings, 104 (99)Tc labeled anti-CEA Fab' studies had a sensitivity of 61% (17 of 28 cases) and a specificity of 91% (69 of 76 cases). In total, (99)Tc labeled anti-CEA Fab' detected 52 of 62 invasive ductal carcinomas, 5 of 5 invasive lobular carcinomas, and 3 of 6 noninvasive tumors (2 ductal carcinomas in situ and 1 intracystic papillary carcinoma). Tumor size significantly affected sensitivity (P = 0.041), with 11 of 14 missed lesions </= T1, and proliferative histology significantly affected specificity (P = 0.012), with 5 of 7 false-positive tumors being premalignant. In 50 breast carcinoma patients, (99)Tc labeled anti-CEA Fab' also demonstrated axillary lymph node involvement regardless of serum CEA levels, with a sensitivity of 80% when more than three lymph nodes were positive. No immune response or other meaningful side effects occurred.

CONCLUSIONS

(99)Tc labeled anti-CEA Fab' had high specificity and positive predictive values for breast carcinoma and the majority of false-positive studies were associated with an increased risk of malignancy. Improved imaging techniques, including dedicated gamma cameras for breast and axillary lymph node imaging, will likely improve the test's sensitivity for smaller lesions.

Safety and efficacy of arcitumomab imaging in colorectal cancer after repeated administration

In pivotal phase III clinical trials for detecting recurrent or metastatic colorectal cancer, most patients received a single arcitumomab injection. However, the early detection of postsurgical recurrence or metastases with arcitumomab will necessitate serial studies for surveillance. We present immunogenicity, safety, and imaging data supporting the use of multiple administrations of arcitumomab.

METHODS

Human antimouse antibody (HAMA) response, adverse events, clinical laboratory values, and diagnostic imaging results were evaluated in 44 patients (24 men, 20 women; age range, 2878 y) after repeated arcitumomab administration (44 second and 3 third injections). Most patients initially had Dukes' class B or C colorectal cancer and had known or occult disease recurrence and elevated serum carcinoembryonic antigen levels at the time of the repeated injection.

RESULTS

At the repeated injection, in no patient did elevated HAMA titers develop, hematology and serum chemistry changes were clinically insignificant, and only 1 adverse event (eosinophilia) was judged at least possibly related to arcitumomab. Arcitumomab imaging results at the second injection were comparable with those obtained in phase III trials after a single injection of arcitumomab, having a 78% per-lesion concordance with CT in the abdomen and pelvis and a 73% sensitivity and 94% specificity based on 9 patients with cancer confirmed surgically at 11 anatomic sites and excluded at 16 sites.

CONCLUSION

These data indicate that at least 2 injections of arcitumomab can be given safely to patients with colorectal cancer, without increased immunogenicity and with imaging efficacy equivalent to the first administration.

Rapid diagnostic imaging of acute, nonclassic appendicitis by leukoscintigraphy with sulesomab, a technetium 99m-labeled antigranulocyte antibody Fab' fragment. LeukoScan Appendicitis Clinical Trial Group

BACKGROUND

The purpose of this study was to evaluate the safety and efficacy of a technetium 99m-labeled antigranulocyte antibody Fab' fragment (sulesomab) as a diagnostic imaging agent in patients with suspected acute, nonclassic appendicitis.

METHODS

This prospective multicenter trial involved 141 children and adults with suspected acute, nonclassic appendicitis. The investigators interpreted planar images acquired 15 to 30 minutes and 1, 2, and 4 hours after injection and also by single-photon emission computed tomography (SPECT). The imaging results were confirmed surgically, whereas nonsurgical patients were considered as not having appendicitis (intent to treat).

RESULTS

Sulesomab had a sensitivity of 91% (29/32 patients) and a negative predictive rate of 97% for acute appendicitis. It detected additional abnormalities in 7 of 9 patients with other inflammatory abdominal disease and had a specificity of 92% (91/99 patients) and a positive predictive value of 80% for surgically confirmed right-lower-quadrant disease. In positive studies, 26% were identified by planar imaging at 15 to 30 minutes, 46% by 1 hour, 63% by 2 hours, and 71% by 4 hours; 29% required SPECT to detect the abnormality. Scanning time was 5 to 10 minutes per planar image and about 45 minutes for a SPECT study. Investigators found that sulesomab would have changed clinical management or reduced additional diagnostic studies in 64% of the patients. Adverse events were infrequent, minor, and self-limiting (9/141 patients, 6%). No human antimurine antibody response occurred in 48 evaluable patients.

CONCLUSIONS

Sulesomab is safe, well-tolerated, and with no apparent immunogenicity. Focal inflammation or infection in the setting of suspected atypical appendicitis is rapidly and accurately detected. Management decisions incorporating sulesomab imaging potentially provide clear patient benefits, especially by correctly predicting surgery to be unnecessary in 97% of patients without acute appendicitis.

Infectious imaging with indium-111-labeled nonspecific polyclonal human immunoglobulin

Nonspecific polyclonal immunoglobulin (IgG), prepared from pooled human serum gamma globulin and labeled with 111In has been reported to be equivalent to antigen-specific antibody in the detection of focal infection or inflammation during the first 24 hr after injection. We describe our experience in a Phase II clinical study using 111In-IgG in 15 patients (8 males, 7 females) ranging from 26 to 80 (mean = 50) yr of age with suspected focal infection/inflammation. Pathologic confirmation was obtained in 5/15 cases. A combination of clinical course, laboratory results, and other imaging procedures were used to categorize the other 10 patients. One possible false-negative involved a presumed aspiration pneumonia in a patient with a history of aspiration, bibasilar infiltrates on chest film, and no other identified source of infection. Otherwise, there were 10 confirmed positives, 4 confirmed negatives, and no false-positives. Our findings confirm earlier reports that 111In-IgG may be a superior imaging agent for infection/inflammation with practical advantages over 67Ga-citrate and 111In-labeled leukocytes.

Diagnostic imaging of musculoskeletal infection. Roentgenography; gallium, indium-labeled white blood cell, gammaglobulin, bone scintigraphy; and MRI

A great deal of effort has been made to evaluate and define the role of various diagnostic imaging techniques in various clinical settings that complicate the diagnosis of osteomyelitis. Except possibly in neonates, bone scintigraphy remains generally recommended when there has been no previous osseous involvement. In other cases of chronic disease, previous fracture or trauma, prosthesis, and diabetic foot, In-WBC scintigraphy is generally accepted as an appropriate imaging technique. MRI will play an increasingly important role in diagnosing osteomyelitis and may prove to be an important adjunct in these cases. Research continues to improve our current diagnostic armamentarium. In-IgG appears to avoid practical deficiencies encountered with 67Ga and In-WBC; it remains to be seen what role this agent will play in routine clinical practice. All agents to date image inflammation, not infection, and most require delayed imaging sessions, usually at 24 hours. These shortcomings necessitate further research to develop new radiotracers that can provide useful images within several hours and that are specific for infection, perhaps ultimately delineating the particular microorganism involved.

Positron emission tomography in the investigation of neuropsychiatric disorders: update and comparison with magnetic resonance imaging and computerized tomography

In many neuropsychiatric disorders, PET imaging offers functional insights unavailable from anatomic imaging alone. Functional deficits may be more extensive than structural findings would indicate, may occur before the detection of anatomic changes, or may even occur in the absence of any structural lesions. We contrast the current role of PET with that of MRI and CT in the investigation of neuropsychiatric disorders including stroke, tumor, head trauma, epilepsy, schizophrenia, movement disorders, normal aging and dementia.

Ventilation-perfusion scintigraphy in an adult with congenital unilateral hyperlucent lung

A variety of congenital and acquired etiologies can give rise to the radiographic finding of a unilateral hyperlucent lung. An unusual case of congenital lobar emphysema diagnosed in a young adult following the initial discovery of a hyperexpanded, hyperlucent lung is reported. Although subsequent bronchoscopy and radiologic studies detailed extensive anatomic abnormalities, functional imaging also played an important role in arriving at this rare diagnosis. In particular, ventilation-perfusion scintigraphy identified the small contralateral lung as the functional lung and helped narrow the differential diagnosis to etiologies involving obstructive airway disorders.

Bilateral deep venous thrombosis in protein S deficiency. Detection by radionuclide venography

Patients with primary hypercoagulopathies often present with recurrent, spontaneous deep venous thrombosis and pulmonary embolism. An adolescent eventually diagnosed with protein S deficiency presented with unilateral deep venous thrombosis documented ultrasonographically. Scintigraphic studies showed no evidence of pulmonary embolism but revealed a complete absence of deep venous flow in both lower extremities, the pelvis, and the abdomen. Subsequent ultrasonography and CT scanning documented this marked thrombotic extension. Radionuclide scintigraphy may play an important role in the serial evaluation of primary hypercoagulable states, particularly when pulmonary scintigraphy is combined with bilateral, lower extremity venography.

Fluorescence recovery spectroscopy as a probe of slow rotational motions

Pump-and-probe techniques can be used to follow the slow rotational motions of fluorescent labels bound to macromolecules in solution. A strong pulse of polarized light initially anisotropically depletes the ground-state population. A continuous low-intensity beam of variable polarization then probes the anisotropic ground-state distribution. Using an additional emission polarizer, the generated fluorescence can be recorded as it rises towards its prepump value. A general theory of fluorescence recovery spectroscopy (FRS) is presented that allows for irreversible depletion processes like photobleaching as well as slowly reversible processes like triplet formation. In either case, rotational motions modulate recovery through cosine-squared laws for dipolar absorption and emission processes. Certain pump, probe, and emission polarization directions eliminate the directional dependence of either dipole and simplify the resulting expressions. Two anisotropy functions can then be constructed to independently monitor the rotations of either dipole. These functions are identical in form to the anisotropy used in fluorescence depolarization measurements and all rotational models developed there apply here with minor modifications. Several setups are discussed that achieve the necessary polarization alignments. These include right-angle detection equipment that is commonly available in laboratories using fluorescence methods.

Separation of translational and rotational contributions in solution studies using fluorescence photobleaching recovery

Although fluorescence photobleaching recovery (FPR) experiments are usually interpreted in terms of the translational motions of a fluorescently labeled species, rotational motions can also modulate recovery through the cosine-squared laws for dipolar absorption and emission processes. In a complex interacting system, translational and rotational contributions may both be simultaneously present. We show how these contributions can be separated in solution studies using an FPR setup in which (a) the linear polarization of the low-intensity observation beam and the high-intensity photobleaching pulse can be varied independently, and (b) all emitted fluorescent photons are counted equally. The fluorescence recovery signal obtained with the observation beam polarized at the magic angle, 54.7 degrees, from the bleach polarization direction is independent of label orientation, whereas the anisotropy function formed from a combination of parallel and perpendicular polarizations isolates the orientational recovery. The anisotropy function is identical to that in fluorescence correlation spectroscopy and, for rigid-body rotational diffusion, can be expressed as a sum of five exponential terms.