A phase 2 study of bevacizumab, erlotinib, and atezolizumab in subjects with advanced hereditary leiomyomatosis and renal cell cancer (HLRCC) associated or sporadic papillary renal cell cancer (pRCC)

TPS4604

Background: Papillary RCC accounts for 10-15% of kidney cancers and is the second most common subtype of RCC after clear cell RCC. HLRCC is a familial cancer syndrome characterized by a propensity for developing papillary kidney cancer. HLRCC-associated renal tumors are known to be clinically aggressive, with a paucity of treatment options. The combination of bevacizumab and erlotinib has shown promising activity in patients with HLRCC-associated RCC and sporadic pRCC (Srinivasan et al, ASCO 2020). We hypothesize that the addition of a PDL-1 inhibitor might provide synergistic clinical activity against these tumors. Methods: This is an ETCTN-sponsored, open-label, multicenter, phase 2 study evaluating bevacizumab, erlotinib and atezolizumab in adult and pediatric patients with advanced 1) HLRCC-associated RCC or 2) sporadic pRCC. Eligible patients will have cytologically or histologically confirmed advanced HLRCC- associated or sporadic pRCC, age ≥12 years, ECOG PS ≤2, no more than two prior regimens targeting the VEGF pathway, no prior treatment with PD-1 or PD-L1 inhibitors and adequate organ and marrow function. Patients with HLRCC-associated RCC or sporadic pRCC will be enrolled into parallel, independent cohorts. Initially, 12 adult patients with advanced HLRCC-associated RCC or sporadic pRCC will be enrolled into the safety run-in portion of the trial. If ≤ 3 dose-limiting toxicities are observed, enrollment will proceed into both cohorts and pediatric patients will be allowed to enroll. A Simon two-stage phase 2 minimax design will be used to determine accrual to each cohort. In the first stage, 12 evaluable patients will be enrolled into cohort 1) HLRCC-associated RCC or cohort 2) sporadic pRCC. If 0 of 12 patients have a CR, then no further patients will be enrolled in that cohort. If 1 or more of the first 12 evaluable patients enrolled have a clinical response, then accrual will continue until a total of 21 evaluable patients (adult or pediatric) have been enrolled into each cohort for a total of 42 patients. Adult patients will receive a fixed dose of bevacizumab (15 mg/kg IV every 21 days) plus atezolizumab (1,200 mg IV every 21 days) and erlotinib (150 mg PO daily). Pediatric patients will receive bevacizumab (15 mg/kg IV every 21 days) plus atezolizumab 15 mg/kg (max 1,200 mg IV every 21 days) and erlotinib 85 mg/m2 (max 150 mg PO daily). The primary endpoint is to assess the complete response rate according to RECIST 1.1 in patients with advanced 1) HLRCC-associated RCC and 2) sporadic pRCC. Secondary endpoints include safety and tolerability, objective response rate, disease control rate, progression-free survival and overall survival. Key exploratory endpoints include evaluation of immunologic modulation associated with this regimen. The study has just opened to accrual. Clinical trial information: NCT04981509.

Phase Ib study of open-label AMG 386 plus paclitaxel (P) and trastuzumab (T) or capecitabine (C) and lapatinib (L) in patients (pts) with HER2+ locally recurrent or metastatic breast cancer (MBC)

529

Background: AMG 386, an investigational peptibody, reduces tumor angiogenesis by blocking interaction of angiopoietins 1 and 2 with the Tie2 receptor. This interim analysis evaluates the tolerability and efficacy of AMG 386 + P/T or C/L in HER2+ MBC. Methods: In part 1, pts in cohorts A1 and A3 (no prior 1st-line MBC T or L ) received AMG 386 IV QW plus P 80 mg/m2 IV QW and T 8 mg/kg loading dose, then 6 mg/kg Q3W; pts in cohorts B1 and B3 (history of failed 1st-line MBC T treatment; no prior L or C) received AMG 386 IV QW plus C 1000 mg/m2 PO Q12 hrs, days 1-14 Q21D and L 1250 mg PO QD. A1 and B1 received AMG 386 at 10 mg/kg; A3 and B3 received AMG 386 at 30 mg/kg. In part 2, cohorts were expanded to n = 20 if ≤ 1 of 6 or ≤ 2 of 9 pts had dose-limiting toxicities (DLTs). Primary endpoints were adverse events (AEs) and DLTs; secondary endpoints included efficacy and pharmacokinetics (PK). Interim results from A1, A3, and B1 will be presented. Results: 46 pts were enrolled at interim analysis; all received ≥ 1 dose of study treatment (A1, A3, B1; n = 20, 6, 20). The median follow-up for A1, A3, and B1 was 39.6, 22.7, and 31.3 wks. Across cohorts, there was 1 DLT in A1. AEs > 50% were peripheral edema, diarrhea, fatigue and alopecia in A1 and A3 combined, and diarrhea, nausea, palmar-plantar erythrodysaesthesia syndrome (PPES), and peripheral edema in B1. AEs grade ≥3 occurring in > 2 pts were peripheral neuropathy, peripheral sensory neuropathy, dyspnea (n = 5, 4, 3, respectively, in A1 and A3 combined); PPES, diarrhea, and neutropenia (n = 6, 5, 3, respectively, in B1). Objective response rates were 80% in A1, 50% in A3, and 50% in B1. Median (95% CI) progression-free survival was 14.5 mo (6.8-20.5) in A1 and 10.1 mo (3.7-14.7) in B1. Median duration of response (DOR) was 12.6 mo (4.3-20.2) in A1 and 8.5 mo (4.1-not evaluable) in B1. PFS and DOR were not yet evaluable in A3. No changes were apparent in any PK parameters in these combinations relative to within study or historical monotherapy PK data. Conclusions: In this ongoing phase 1b study of pts with HER2+ MBC, interim results suggest that adding AMG 386 to P/T or C/L is tolerable and has antitumor activity. Updated data will be presented.

Characterization of the isolated rat flexor digitorum brevis for the study of skeletal muscle phosphorylase kinase phosphorylation

The flexor digitorum brevis skeletal muscle, a nearly homogeneous fast-twitch oxidative glycolytic fiber type, has been examined for its suitability to explore the regulation of phosphorylase kinase by multisite phosphorylation. A characterization of the adrenergic response of glycogenolytic enzymes, together with the previous data on contractile properties (Carlsen, R. C., Larson, D. B., and Walsh, D. A. (1985) Can. J. Physiol. Pharm. 63, 958-965), has demonstrated that this muscle is stably maintained for the several hours necessary for phosphorylation studies. The phosphorylase kinase in this muscle is primarily the alpha' isozyme, suggesting that the alpha versus alpha' isozyme distribution in muscle is related more to oxidative capacity than to fiber contractile characteristics. Using this muscle system, beta-adrenergic activation of phosphorylase kinase was observed to occur with concomitant phosphorylation of both the alpha' and beta subunits, with the total in the alpha' subunit being approximately 3-fold greater. Similarly, deactivation, following initial adrenergic activation, occurred concomitantly with the dephosphorylation of the two subunits. These results are compatible with the conclusions drawn from previous studies of the isolated enzyme and of the enzyme in perfused rat cardiac muscle, that both alpha' (or alpha) and beta subunit phosphorylation regulate phosphorylase kinase activity.

Subunit phosphorylation and activation of skeletal muscle phosphorylase kinase by the cAMP-dependent protein kinase. Divalent metal ion, ATP, and protein concentration dependence

This report provides a characterization of the effects of varying the concentrations of Mg2+, ATP, phosphorylase kinase, and the cAMP-dependent protein kinase on the activation and phosphorylation of phosphorylase kinase. The results show the following. (a) The Km for MgATP2- for the cAMP-dependent protein kinase-catalyzed phosphorylation is decreased by increasing Mg2+, probably as a consequence of decreasing the free ATP:MgATP2- ratio and increasing free Mg2+. (b) Whereas beta subunit phosphorylation of phosphorylase kinase plays a prominent role in determining its activity, alpha subunit phosphorylation can also modulate activity. (c) The phosphorylation of the alpha subunit, which occurs following the initial cAMP-dependent phosphorylation of the beta subunit, is catalyzed by the cAMP-dependent protein kinase and is not a consequence of EGTA-insensitive (or EGTA-sensitive) autophosphorylation occurring as a result of the enhanced phosphorylase kinase activity. (d) The relationship between subunit phosphorylation and phosphorylase kinase activation is complex and particularly dependent upon concentrations of cAMP-dependent protein kinase and phosphorylase kinase in the activation reaction. The data suggest the possibilities that the pathway of phospho-intermediates involved in the activation process probably varies with the activation conditions, that the efficacy of a specific site to be covalently modified is dependent upon the phosphorylation status of other sites, and that the effect of phosphorylation in regulating activity may also be dependent on the phosphorylation status of other sites. It is clear from the data that the activation process for phosphorylase kinase can be very complex, and it is possible that this complexity might have significant physiological ramifications.