SGNTUC-019: Phase 2 basket study of tucatinib and trastuzumab in previously treated solid tumors with HER2 alterations (trial in progress)

TPS3151

Background: Tucatinib (TUC) is a highly selective HER2-directed TKI approved in combination with trastuzumab (Tras) and capecitabine (Cape) for HER2 overexpressed/amplified (HER2+) metastatic breast cancer (BC), based on a statistically significant and clinically meaningful PFS, OS, and ORR benefit over Tras and Cape. In xenograft models of HER2+ and HER2-mutated (HER2-mut) tumors, dual targeting of HER2 with TUC and Tras showed superior activity to either agent alone. While various HER2-directed agents have been evaluated in HER2+ and HER2-mut tumors, there are no approved HER2 therapies outside of breast and gastric cancers. The SGNTUC-019 basket study is evaluating TUC combined with Tras in patients (pts) with HER2+ or HER2-mut locally-advanced unresectable or metastatic solid tumors. Methods: SGNTUC-019 (NCT04579380) is a multi-cohort, open-label, international phase 2 study. Eligible pts must have progressed on or after the last systemic therapy for advanced disease. Metastatic cervical cancer: must have received platinum-based chemotherapy ± bevacizumab; hormone receptor positive (HR+) HER2-mut BC: must have received a prior CDK4/6 inhibitor. Pts must be ≥18 years old, with ECOG PS ≤1, adequate hepatic, hematological, renal, coagulation, and cardiac function, and no prior HER2-directed therapy (except Tras for uterine serous carcinoma). For eligibility, HER2 alterations can be demonstrated by HER2+ in tumor tissue by prior IHC/ISH (IHC 3+/signal ratio ≥2.0 or gene copy number >6), or by HER2 amplification/mutation in a prior or on-study NGS assay of ctDNA or prior tissue NGS assay. Pts with HER2+ disease will be enrolled in cohorts for cervical, uterine, biliary tract, and urothelial cancers, non-squamous NSCLC, and other solid tumors (except GEC, BC, and CRC). Pts with HER2-mut disease will be enrolled in cohorts for non-squamous NSCLC, BC, and other solid tumors. Except for solid tumor and BC cohorts, 12 RECIST 1.1 evaluable pts will be enrolled in each cohort. If ≥2 responses are observed, the cohort will be expanded to a total of 30 pts. Other solid tumor and BC cohorts will enroll 30 pts in a single stage. If justified, additional HER2+ or HER2-mut disease-specific cohorts may be opened. Approximately 162-270 pts are planned. The primary objective is antitumor activity in each cohort, with confirmed ORR per investigator as primary endpoint, and disease control rate, duration of response, PFS, and OS as secondary endpoints. Pts will receive TUC 300 mg orally twice daily and Tras 8 mg/kg IV on Cycle 1 Day 1 and 6 mg/kg q21 days from Cycle 2 Day 1. HR+ BC pts will also receive fulvestrant 500 mg IM every 4 weeks and C1 D15. Disease assessments per RECIST 1.1 will occur q6 weeks for 24 weeks, then q12 weeks. TUC PK will be evaluated in all pts in Cycles 2-6. QoL is evaluated q2 cycle using EQ-5D-5L. Sites are open in the US; EU and Asia will be opened. Enrollment began in Dec 2020. Clinical trial information: NCT04579380.

SGNTUC-019: Phase II basket study of tucatinib (TUC) and trastuzumab (Tras) in previously treated solid tumors with HER2 alterations: Urothelial cancer cohort (trial in progress)

TPS499

Background: Tucatinib (TUC), a highly selective HER2-directed TKI recently approved for HER2 overexpressed/amplified (HER2+) metastatic breast cancer, is being developed as a novel therapy for patients (pts) with metastatic CRC, gastric cancer, and other GI tumors. In xenograft models of HER2+ and HER2-mutated (HER2-mut) tumors, dual targeting of HER2 with TUC and trastuzumab (Tras) showed superior activity to either agent alone. Despite the development of several new therapies for metastatic urothelial cancer, response durations generally remain short and the great majority of pts succumb to the disease, highlighting the need for therapeutic approaches. Given that 20-30% of urothelial cancers have molecular alterations of the ErbB family, TUC in combination with Tras warrants further evaluation in this population. The SGNTUC-019 basket study is evaluating TUC in combination with Tras in pts with HER2+ or HER2-mut solid tumors, including a cohort of pts with locally advanced or metastatic (LAUM) urothelial cancer. Methods: SGNTUC-019 (NCT04579380) is a multi-cohort, open-label, international phase II study evaluating pts with previously treated solid tumors displaying HER2 overexpression/amplification or activating mutations. Eligible pts must have HER2+ or HER2-mut LAUM solid tumors, with progression on or after the last systemic therapy for advanced disease. Pts must be ≥18 years old, with ECOG PS ≤1, adequate hepatic, hematological, renal, coagulatory, and cardiac function, and no prior exposure to HER2-directed therapy. For eligibility, HER2 alterations can be demonstrated by HER2 overexpression/amplification in tumor tissue by prior IHC/ISH (IHC 3+/signal ratio ≥2.0 or gene copy number >6), or by HER2 amplification/mutation in a prior or on-study NGS assay of ctDNA or prior tissue NGS assay. The HER2 overexpression/amplification urothelial cancer cohort will enroll 12 RECIST 1.1 response-evaluable pts. If ≥2 responses are observed, the cohort will be expanded to a total of 30 pts. Pts with HER2-mut urothelial cancer will be enrolled in a cohort of 30 pts for all solid tumor types except breast cancer and non-squamous NSCLC. If justified, a separate cohort for HER2-mut urothelial cancer may be opened. The primary objective is antitumor activity in each cohort, with confirmed ORR as primary endpoint, and disease control rate, duration of response, PFS, and OS as secondary endpoints. Pts will receive TUC 300 mg orally twice daily and Tras 8 mg/kg IV on Cycle 1 Day 1 and 6 mg/kg q21 days from Cycle 2 Day 1. Disease assessments per RECIST 1.1 will occur q6 weeks for 24 weeks, then q12 weeks. Trough concentrations of TUC will be evaluated in all pts in Cycles 2-6, with a peak concentration sampled in Cycle 3. Quality of life will be evaluated q2 cycle using EQ-5D-5L. Sites will open in the US, EU, and Asia; enrollment is anticipated to begin in Dec 2020. Clinical trial information: NCT04579380.

Tucatinib Inhibits Renal Transporters OCT2 and MATE Without Impacting Renal Function in Healthy Subjects

Tucatinib is a potent tyrosine kinase inhibitor selective for human epidermal growth factor receptor 2 (HER2) approved by the US Food and Drug Administration for the treatment of HER2‐positive metastatic breast cancer and in development for other HER2‐positive solid tumors. Modest, reversible serum creatinine (SCr) elevations have been observed in tucatinib clinical trials. SCr is conveyed by the renal drug transporters organic cation transporter 2 (OCT2) and multidrug and toxin extrusion protein 1 (MATE1) and 2‐K (MATE2‐K) and can increase in the presence of inhibitors of these transporters. In vitro, tucatinib inhibited OCT2‐, MATE1‐, and MATE2‐K‐mediated transport of metformin, with IC₅₀ values of 14.7, 0.340, and 0.135 µM, respectively. Tucatinib also inhibited OCT2‐ and MATE1‐mediated transport of creatinine, with IC₅₀ values of 0.107 and 0.0855 µM, respectively. A phase 1 study with metformin administered orally in the absence and presence of tucatinib was conducted in 18 healthy subjects. Renal function was assessed by measuring glomerular filtration rate (GFR; based on iohexol plasma clearance) and endogenous markers (SCr, cystatin C‐based estimated glomerular filtration rate [eGFR]) with and without tucatinib. Metformin exposure increased (1.4‐fold) and renal clearance decreased (29.99‐17.64 L/h) with tucatinib, with no effect on metformin maximum concentration. Creatinine clearance transiently decreased 23% with tucatinib. GFR and eGFR, which are unaffected by OCT2 and/or MATE1/2‐K transport, were unchanged with tucatinib. These data demonstrate that tucatinib inhibits OCT2‐ and MATE1/2‐K‐mediated tubular secretion of creatinine, which may manifest as mild SCr elevations that are not indicative of renal impairment.

PX-866 and docetaxel in patients with advanced solid tumors

3024

Background: PX-866, an irreversible pan-isoform inhibitor of Class 1 PI-3K has additive to synergistic effects when combined with docetaxel in xenograft models of NSCLC and SCCHN. A phase I/II study of PX-866 and docetaxel was initiated to further evaluate this combination. Enrollment in phase I is complete, and the randomized, controlled phase II portion is now enrolling patients with either NSCLC or SCCHN. Phase I safety and pharmacokinetics were previously described; the recommended phase II dose of PX-866 was 8 mg daily, the same as the single agent MTD (Jimeno A, et al. AACR-NCI-EORTC, 2011). Updated phase I antitumor and biomarker results are presented here. Methods: Phase 1 consisted of dose escalation of PX-866 at 4, 6, or 8 mg po qd in combination with docetaxel 75 mg/m2 IV once every 21 days (d). Patients had advanced solid tumors for which docetaxel was compendia listed. Tumor restaging was performed every 2 cycles. Archived tumor biopsies were collected for assessment of potential biomarkers of response, including PIK3CA and KRAS mutations and PTEN expression. Results: 43 pts were enrolled: NSCLC (n=6), prostate (n=5), ovarian (n=5), SCCHN (n=3), and pancreatic (n=3) were the most common tumor types. Median time on study (TOS) was 81 d (5-361), with 9 pts still on study. 16 pts received ≥ 6 cycles (6-17), including 3 pts with NSCLC, and 4 pts with ovarian cancer. Biomarker data are available for 20 evaluable pts. Median days on study by mutational status was: PIK3CA/KRAS WT (n=13): 91 d (28-286); PIK3CA-MUT (n=5): 183 d (64-342); KRAS-MUT (n=3): 141 d (125-361); and PIK3CA/KRAS-MUT (n=2): 96 d (86-105). A trend toward longer TOS was observed in pts with PIK3CA-MUT vs PIK3CA/KRAS-WT (p=0.14). Assessment of PTEN is ongoing. Best response in 32 evaluable pts was 2 PR (6%), 22 SD (69%), and 8 PD (25%). The PRs were in NSCLC and ovarian cancer (both PIK3CA/KRAS WT). 8 other pts had ≥15% tumor shrinkage, including NSCLC (n=2). Conclusions: PX-866 with docetaxel was associated with a disease control rate of 75%, with 50% of evaluable pts demonstrating SD or better for ≥ 6 cycles. Based on available data, a trend for a longer TOS was seen with PIK3CA-MUT pts. This relationship will be further evaluated in phase II.

Late relapse of myelodysplasia after allogeneic transplantation concomitant with new presentation of invasive liposarcoma as a secondary neoplasm

Second malignancies are uncommon events in the survivors of allogeneic transplant procedures, although they are increased compared to normal control populations. Among these malignancies, sarcomas are exceedingly rare. In addition, relapse of primary myelodysplasia rarely occurs after 5 years from the time of allogeneic transplantation. This report describes an unusual presentation of liposarcoma with concomitant relapse of underlying myelodysplasia developing in a patient 9 years after the first of two allogeneic transplantations.

Developmental study of chondroitin-6-sulphate in normal and dystrophic rat retina

The RCS rat is a widely studied model of human retinal dystrophies including retinitis pigmentosa. Chondroitin-6-sulphate (C6S) in the interphotoreceptor matrix was localised immunocytochemically in both the normal congenic and dystrophic strains of the RCS rat up to 65 days postnatally. From postnatal days 5 to 15 the distribution of C6S in both strains was similar, being localised in the interstices of developing inner and outer segments and adjacent to the RPE surface. In the normal rats, the distribution of C6S did not change with age. In the RCS rats, however, at postnatal days 20 to 35 staining was observed as a dense band at the junction of inner and outer segments and no staining was observed adjacent to the surface of the RPE. At postnatal day 45 onwards there was a decrease and a complete absence of C6S staining in these rats. This change in the pattern of staining correlated with the morphological observation of the progressive degeneration of photoreceptor cells suggesting that C6S may be important in photoreceptor degeneration in the RCS rat.

Cytotoxic effects of residual chemicals from polymeric biomaterials for artificial soft intraocular lenses

Development of improved hydrogels for soft intraocular lenses, based on 2-hydroxyethyl methacrylate monomer, requires the use of various other monomers and polymerization additives which have potential ocular toxicity. Three monomers, 2-hydroxyethyl methacrylate, methyl methacrylate, and 2-ethoxyethyl methacrylate, as well as two common inhibitors, hydroquinone and 4-methoxyphenol, were subjected to in vitro cytotoxicity assays as aqueous solutions at different concentrations. A new polymerization initiator, 2,2'-azo-bis-(2,4-dimethyl valeronitrile), was thermally decomposed in water at different concentrations and the products were also assayed for cytotoxicity. Assays were based on incubation with human choroidal fibroblasts. Cell death was evaluated by trypan blue dye exclusion, DNA synthesis inhibition, and lactate dehydrogenase tests. While methyl methacrylate and 2-ethoxyethyl methacrylate were found nontoxic, the other chemicals displayed high cytotoxicity. However, when extracts of synthesized poly(2-hydroxyethyl methacrylate) specimens, differentially treated after polymerization, were subjected to the same assays it was found that toxicity from residual 2-hydroxyethyl methacrylate monomer was lost during steam sterilization and storage in water because of the removal of the monomer through aqueous washing. The lack of toxicity in these specimens suggests that residual contents of inhibitor and initiator are too low to cause toxic effects on choroidal fibroblasts. It is concluded that hydrogels have low cytotoxic effects in vitro.

Subretinal new vessel recurrence in age-related macular degeneration

Laser photocoagulation with argon or krypton is currently used to treat selected patients with age-related macular degeneration and sudden visual loss from subretinal new vessel formation. In 102 consecutive cases, treated over two years, closure of the vessels was achieved without additional major visual loss in 79% when assessed at two months. Early failure occurred in 21% and was due either to selection of cases with central location or failure to close the new vessel. Later failures due to recurrent subretinal new vessel formation or progression of other macular degenerative changes has occurred in a further 28% so far. Although controlled clinical trials show a significant benefit of treatment, the overall impact of these few successes on the population with macular degeneration is small. Further understanding of the mechanism of subretinal new vessel formation is urgently required. Areas under investigation include the response of injured retinal pigment epithelium, choroid and retina and cellular production of facilitatory factors including proteases and fibronectin.

False-negative bone image with radiographically evident osteoblastic lesions in prostatic carcinoma

A unique case of documented prostatic carcinoma with radiographically evident osteoblastic lesions and a false-negative bone image is presented.

Morphology and cell kinetics of fatty streak lesion formation in the hypercholesterolemic rabbit

The rationale for this study was to determine whether in the hypercholesterolemic rabbit any evidence of endothelial injury could be detected prior to or during the early phase of fatty intimal lesion formation. The data presented showed that in the first 12 weeks of feeding a 0.1% cholesterol-rich diet, rabbit aortas were covered with an intact endothelium. Focal areas of increased endothelial cell replication were observed adjacent to the aortic ostia at 12 and 20 weeks. These replicating cells were almost exclusively located at the shoulders of large raised lesions. In a similar fashion, adherent leukocytes were observed adjacent to the aortic ostia, and at later times they were concentrated at the periphery of these intimal lesions. Smooth muscle cell replication, as assessed by autoradiography, was found to be significantly increased only after 20 weeks of feeding the lipid-rich diet. These data suggest that an increased endothelial cell turnover and leukocyte adhesion were the first detectable changes induced by cholesterol feeding and that smooth muscle cell proliferation occurred soon after these events.

Production of platelet-derived growth factor-like molecules by cultured arterial smooth muscle cells accompanies proliferation after arterial injury

The migration and proliferation of smooth muscle cells (SMCs) within the intima of arteries following mechanical injury is thought to be initiated by vessel wall injury and release of growth factors, in particular the platelet-derived growth factor (PDGF). However, the mechanism by which SMC proliferation is regulated after platelet interaction with the vessel wall has ceased is unknown. Here we show that SMCs derived from the intima of injured rat arteries (intimal SMCs) are phenotypically distinct from SMCs from unmanipulated vessels (medial SMCs). Intimal SMCs secrete 5-fold greater amounts of PDGF-like activity into conditioned medium in culture, have fewer receptors for 125I-labeled PDGF, and are not mitogenically stimulated by exogenous purified PDGF. This study demonstrates that two SMC phenotypes can develop in the adult rat artery and suggests that SMC proliferation in vivo may be controlled, in part, by SMCs that produce PDGF-like molecules.

Immunohistochemical studies of C-reactive protein and apolipoprotein B in inflammatory and arterial lesions

Interactions in vivo between C-reactive protein (CRP) and apolipoprotein B (apo-B)-containing lipoproteins were sought in inflammatory lesions and atherosclerosis. CRP was demonstrated immunohistochemically on the surface of some muscle fibres in locally induced inflammatory lesions in the rabbit, but apoB was not detected in the same distribution. CRP was not detected in catheter-induced aortic endothelial injuries in the rabbit, in arterial lesions containing apoB from cholesterol-fed rabbits, in apoB-containing human fatty streaks or in advanced human atherosclerotic lesions.

Endothelial healing in the rabbit aorta and the effect of risk factors for atherosclerosis. Hypercholesterolemia

The effect of diet-induced moderate hypercholesterolemia on endothelial healing has been investigated in the rabbit following a narrow superficial injury to aortic endothelium without damage to the media of the vessel. The healing process was compared with that observed in normocholesterolemic animals. The degree of platelet involvement was similar in both normo- and hypercholesterolemic animals. Reendothelialization occurred within 48 hours in both groups of animals, showing that hypercholesterolemia did not delay endothelial healing. It was found that esterase-positive cells, which morphologically resembled monocyte-macrophages, adhered to and penetrated regenerated endothelium only in hypercholesterolemic animals. After reendothelialization in normocholesterolemic animals, there was no increase in the number of cells within the intima of the vessel and no evidence of lipid accumulation. In hypercholesterolemic animals, cells accumulated in the intima in areas of regeneration, and lipid accumulation occurred within both the intima and the media in areas of regeneration.

Endothelial healing following defined injury to rabbit aorta. Depth of injury and mode of repair

A study has been made of the healing of a narrow deep injury to rabbit aortic endothelium which also involves damage to the media of the vessel. The injury was produced using a nylon catheter containing a wire filament; the injury was approximately 150 micron in width and damaged up to 3 elastic lamellae. Immediately after injury platelet aggregates were observed over the injured areas, several hours later large numbers of leukocytes were also seen to adhere. Two days after injury a non-thrombogenic neointimal surface was observed over deeply injured areas; endothelial cells could be identified covering the injured area at 6 days. The healing process following the injury has been directly compared with the healing of rabbit aortic endothelium following a superficial injury of similar width, where endothelial cells are removed without significant damage to the media of the vessel [1]. The results show that (a) following a narrow injury to the aorta which causes damage to the media platelet aggregation and proliferation of smooth muscle cells occurs, (b) despite the disruption of subendothelial components, endothelium rapidly regenerates over the narrow injured area, although not as quickly as for a superficial injury.

Narrow superficial injury to rabbit aortic endothelium. The healing process as observed by scanning electron microscopy

A study was made of the healing of aortic endothelium in rabbits following the production of a defined superficial injury. This was induced using a fine nylon filament which removed the endothelial cells without producing significant damage to underlying structures. The morphology of the injury and subsequent repair was observed using light microscopy and scanning and transmission electron microscopy. Two forms of injury were produced (a) a longitudinal injury along the full length of the aorta which was 50-80 microns wide (about 5-8 cell widths), (b) a circumferential injury approximately 80 microns wide (about 2 cell lengths). Thirty minutes after injury the exposed tissue was almost devoid of adherent cells, but after 4 h became covered by a sparse monolayer of platelets. Occasional leukocytes were also present from 7 h after injury. Injury tracks were found to repair very quickly; re-endothelialisation being complete by 48 h and there being no sign of injury by 7 days.