The Use of Microdosing for In vivo Phenotyping of Cytochrome P450 Enzymes: Where Do We Stand? A Narrative Review

Cytochrome P450 (CYP) enzymes play a central role in the elimination of approximately 80% of all clinically used drugs. Differences in CYP enzyme activity between individuals can contribute to interindividual variability in exposure and, therefore, treatment outcome. In vivo CYP enzyme activity could be determined with phenotyping. Currently, (sub)therapeutic doses are used for in vivo phenotyping, which can lead to side effects. The use of microdoses (100 µg) for in vivo phenotyping for CYP enzymes could overcome the limitations associated with the use of (sub)therapeutic doses of substrates. The aim of this review is to provide a critical overview of the application of microdosing for in vivo phenotyping of CYP enzymes. A literature search was performed to find drug-drug interaction studies of CYP enzyme substrates that used microdoses of the respective substrates. A substrate was deemed sensitive to changes in CYP enzyme activity when the pharmacokinetics of the substrate significantly changed during inhibition and induction of the enzyme. On the basis of the currently available evidence, the use of microdosing for in vivo phenotyping for subtypes CYP1A2, CYP2C9, CYP2D6, and CYP2E1 is not recommended. Microdosing can be used for the in vivo phenotyping of CYP2C19 and CYP3A. The recommended microdose phenotyping test for CYP2C19 is measuring the omeprazole area-under-the-concentration-time curve over 24 h (AUC0-24) after administration of a single 100 µg dose. CYP3A activity could be best determined with a 0.1-75 µg dose of midazolam, and subsequently measuring AUC extrapolated to infinity (AUC∞) or clearance. Moreover, there are two metrics available for midazolam using a limited sampling strategy: AUC over 10 h (AUC0-10) and AUC from 2 to 4 h (AUC2-4).

Is Higher Docetaxel Clearance in Prostate Cancer Patients Explained by Higher CYP3A? An In Vivo Phenotyping Study with Midazolam

Patients with prostate cancer (PCa) have a lower docetaxel exposure for both intravenous (1.8-fold) and oral administration (2.4-fold) than patients with other solid cancers, which could influence efficacy and toxicity. An altered metabolism by cytochrome P450 3A (CYP3A) due to castration status might explain the observed difference in docetaxel pharmacokinetics. In this in vivo phenotyping, pharmacokinetic study, CYP3A activity defined by midazolam clearance (CL) was compared between patients with PCa and male patients with other solid tumors. All patients with solid tumors who did not use CYP3A-modulating drugs were eligible for participation. Patients received 2 mg midazolam orally and 1 mg midazolam intravenously on 2 consecutive days. Plasma concentrations were measured with a validated liquid chromatography-tandem mass spectrometry method. Genotyping was performed for CYP3A4 and CYP3A5. Nine patients were included in each group. Oral midazolam CL was 1.26-fold higher in patients with PCa compared to patients with other solid tumors (geometric mean [coefficient of variation], 94.1 [33.5%] L/h vs 74.4 [39.1%] L/h, respectively; P = .08). Intravenous midazolam CL did not significantly differ between the 2 groups (P = .93). Moreover, the metabolic ratio of midazolam to 1'-hydroxy midazolam did not differ between the 2 groups for both oral administration (P = .67) and intravenous administration (P = .26). CYP3A4 and CYP3A5 genotypes did not influence midazolam pharmacokinetics. The observed difference in docetaxel pharmacokinetics between both patient groups therefore appears to be explained neither by a difference in midazolam CL nor by a difference in metabolic conversion rate of midazolam.

Pharmacokinetic boosting of olaparib: A randomised, cross-over study (PROACTIVE-study)

BACKGROUND

Pharmacokinetic (PK) boosting is the intentional use of a drug-drug interaction to enhance systemic drug exposure. PK boosting of olaparib, a CYP3A-substrate, has the potential to reduce PK variability and financial burden. The aim of this study was to investigate equivalence of a boosted, reduced dose of olaparib compared to the non-boosted standard dose.

METHODS

This cross-over, multicentre trial compared olaparib 300 mg twice daily (BID) with olaparib 100 mg BID boosted with the strong CYP3A-inhibitor cobicistat 150 mg BID. Patients were randomised to the standard therapy followed by the boosted therapy, or vice versa. After seven days of each therapy, dense PK sampling was performed for noncompartmental PK analysis. Equivalence was defined as a 90% Confidence Interval (CI) of the geometric mean ratio (GMR) of the boosted versus standard therapy area under the plasma concentration-time curve (AUC0-12 h) within no-effect boundaries. These boundaries were set at 0.57-1.25, based on previous pharmacokinetic studies with olaparib capsules and tablets.

RESULTS

Of 15 included patients, 12 were eligible for PK analysis. The GMR of the AUC0-12 h was 1.45 (90% CI 1.27-1.65). No grade ≥3 adverse events were reported during the study.

CONCLUSIONS

Boosting a 100 mg BID olaparib dose with cobicistat increases olaparib exposure 1.45-fold, compared to the standard dose of 300 mg BID. Equivalence of the boosted olaparib was thus not established. Boosting remains a promising strategy to reduce the olaparib dose as cobicistat increases olaparib exposure Adequate tolerability of the boosted therapy with higher exposure should be established.

WEE1 inhibitor adavosertib in combination with carboplatin in advanced TP53 mutated ovarian cancer: A biomarker-enriched phase II study

OBJECTIVE

In the first part of this phase II study (NCT01164995), the combination of carboplatin and adavosertib (AZD1775) was shown to be safe and effective in patients with TP53 mutated platinum-resistant ovarian cancer (PROC). Here, we present the results of an additional safety and efficacy cohort and explore predictive biomarkers for resistance and response to this combination treatment.

METHODS

This is a phase II, open-label, non-randomized study. Patients with TP53 mutated PROC received carboplatin AUC 5 mg/ ml·min intravenously and adavosertib 225 mg BID orally for 2.5 days in a 21-day cycle. The primary objective is to determine the efficacy and safety of carboplatin and adavosertib. Secondary objectives include progression-free survival (PFS), changes in circulating tumor cells (CTC) and exploration of genomic alterations.

RESULTS

Thirty-two patients with a median age of 63 years (39-77 years) were enrolled and received treatment. Twenty-nine patients were evaluable for efficacy. Bone marrow toxicity, nausea and vomiting were the most common adverse events. Twelve patients showed partial response (PR) as best response, resulting in an objective ORR of 41% in the evaluable patients (95% CI: 23%-61%). The median PFS was 5.6 months (95% CI: 3.8-10.3). In patients with tumors harboring CCNE1 amplification, treatment efficacy was slightly but not significantly better.

CONCLUSIONS

Adavosertib 225 mg BID for 2.5 days and carboplatin AUC 5 could be safely combined and showed anti-tumor efficacy in patients with PROC. However, bone marrow toxicity remains a point of concern, since this is the most common reason for dose reductions and dose delays.

Beyond Skin Rash: Alpelisib-Induced Anaphylactic Reactions

Alpelisib is a specific oral PI3K inhibitor used combined with fulvestrant for the treatment of patients with HR+/HER2-/PIK3CA-mutated metastatic breast cancer. Adverse drug reactions with alpelisib are common, including hyperglycemia and rash. Here we describe extraordinary and life-threatening reactions beyond skin rash in two patients with progressive PIK3CA-mutated metastatic cancer in whom alpelisib was initiated. Case-A (vaginal cancer): After 10 days on treatment, she developed dry eyes, generalized rash and itching. Alpelisib was interrupted and symptomatic treatment initiated. Because of an initial tumor response, a rechallenge was done. Ninety minutes after a reduced dose of alpelisib, she developed an anaphylactic reaction with angioedema, hypotension, and skin rash. Case-B (breast cancer): After 11 days on treatment, she developed skin rash and alpelisib was interrupted. At re-initiation, she felt tingles in her face and ears and some skin erythema. Given the mild rash, a second rechallenge with premedication was performed. Ninety minutes after a reduced dose of alpelisib, she developed a type-1 allergic reaction with angioedema, tingles, and skin rash. In both cases, a type-1 allergic reaction was diagnosed and symptomatic treatment was initiated, alpelisib was permanently discontinued and the patients fully recovered the next week(s). This report underlines the critical importance to consider type-I allergic reactions in the differential diagnosis in cases of rash associated with alpelisib. Even if a reaction develops after days on treatment, a type-I allergic reaction cannot be excluded. A rechallenge can be dangerous and should always be well contemplated or even avoided.

Efficacy, safety and biomarker analysis of durvalumab in patients with mismatch-repair deficient or microsatellite instability-high solid tumours

BACKGROUND

In this study we aimed to evaluate the efficacy and safety of the PD-L1 inhibitor durvalumab across various mismatch repair deficient (dMMR) or microsatellite instability-high (MSI-H) tumours in the Drug Rediscovery Protocol (DRUP). This is a clinical study in which patients are treated with drugs outside their labeled indication, based on their tumour molecular profile.

PATIENTS AND METHODS

Patients with dMMR/MSI-H solid tumours who had exhausted all standard of care options were eligible. Patients were treated with durvalumab. The primary endpoints were clinical benefit ((CB): objective response (OR) or stable disease ≥16 weeks) and safety. Patients were enrolled using a Simon like 2-stage model, with 8 patients in stage 1, up to 24 patients in stage 2 if at least 1/8 patients had CB in stage 1. At baseline, fresh frozen biopsies were obtained for biomarker analyses.

RESULTS

Twenty-six patients with 10 different cancer types were included. Two patients (2/26, 8%) were considered as non-evaluable for the primary endpoint. CB was observed in 13 patients (13/26, 50%) with an OR in 7 patients (7/26, 27%). The remaining 11 patients (11/26, 42%) had progressive disease. Median progression-free survival and median overall survival were 5 months (95% CI, 2-not reached) and 14 months (95% CI, 5-not reached), respectively. No unexpected toxicity was observed. We found a significantly higher structural variant (SV) burden in patients without CB. Additionally, we observed a significant enrichment of JAK1 frameshift mutations and a significantly lower IFN-γ expression in patients without CB.

CONCLUSION

Durvalumab was generally well-tolerated and provided durable responses in pre-treated patients with dMMR/MSI-H solid tumours. High SV burden, JAK1 frameshift mutations and low IFN-γ expression were associated with a lack of CB; this provides a rationale for larger studies to validate these findings.

TRIAL REGISTRATION

Clinical trial registration: NCT02925234. First registration date: 05/10/2016.

First-in-human phase I study of the OX40 agonist GSK3174998 with or without pembrolizumab in patients with selected advanced solid tumors (ENGAGE-1)

BACKGROUND

The phase I first-in-human study ENGAGE-1 evaluated the humanized IgG1 OX40 agonistic monoclonal antibody GSK3174998 alone (Part 1 (P1)) or in combination with pembrolizumab (Part 2 (P2)) in patients with advanced solid tumors.

METHODS

GSK3174998 (0.003-10 mg/kg) ± pembrolizumab (200 mg) was administered intravenously every 3 weeks using a continuous reassessment method for dose escalation. Primary objectives were safety and tolerability; secondary objectives included pharmacokinetics, immunogenicity, pharmacodynamics, and clinical activity.

RESULTS

138 patients were enrolled (45 (P1) and 96 (P2, including 3 crossovers)). Treatment-related adverse events occurred in 51% (P1) and 64% (P2) of patients, fatigue being the most common (11% and 24%, respectively). No dose-toxicity relationship was observed, and maximum-tolerated dose was not reached. Dose-limiting toxicities (P2) included Grade 3 (G3) pleural effusion and G1 myocarditis with G3 increased troponin. GSK3174998 ≥0.3 mg/kg demonstrated pharmacokinetic linearity and >80% receptor occupancy on circulating T cells; 0.3 mg/kg was selected for further evaluation. Limited clinical activity was observed for GSK3174998 (P1: disease control rate (DCR) ≥24 weeks 9%) and was not greater than that expected for pembrolizumab alone (P2: overall response rate 8%, DCR ≥24 weeks 28%). Multiplexed immunofluorescence data from paired biopsies suggested that increased infiltration of natural killer (NK)/natural killer T (NKT) cells and decreased regulatory T cells (Tregs) in the tumor microenvironment may contribute to clinical responses: CD16+CD56-CD134+ NK /NKT cells and CD3+CD4+FOXP3+CD134+ Tregs exhibited the largest magnitude of change on treatment, whereas CD3+CD8+granzyme B+PD-1+CD134+ cytotoxic T cells were the least variable. Tumor gene expression profiling revealed an upregulation of inflammatory responses, T-cell proliferation, and NK cell function on treatment with some inflammatory cytokines upregulated in peripheral blood. However, target engagement, evidenced by pharmacologic activity in peripheral blood and tumor tissue, did not correlate with clinical efficacy. The low number of responses precluded identifying a robust biomarker signature predictive of response.

CONCLUSIONS

GSK3174998±pembrolizumab was well tolerated over the dose range tested and demonstrated target engagement. Limited clinical activity does not support further development of GSK3174998±pembrolizumab in advanced cancers.

TRIAL REGISTRATION NUMBER

NCT02528357.

Abstract CT033: Inducible T cell costimulatory (ICOS) receptor agonist, feladilimab (FE), alone and in combination (combo) with pembrolizumab (PE): Results from INDUCE-1 relapsed/refractory (R/R) melanoma expansion cohorts (EC)

Background: INDUCE-1 is a first-in-human trial investigating FE, an IgG4 ICOS agonist non-T-cell depleting mAb, in monotherapy (mono) and combo with PD-1 inhibitor PE. ICOS is highly expressed in melanoma, an immunotherapy responsive tumor, and is a biomarker of response to anti-CTLA-4 treatment; in nonclinical models, ICOS agonism has enhanced activity in combo with immune checkpoint blockade (ICB). Preliminary data from INDUCE-1 R/R melanoma ECs are presented to support FE expansion in ICB experienced (exp) R/R melanoma patients (pts).

Methods: Eligible pts had non-uveal R/R melanoma, ≤5 prior lines of systemic therapy, achieved response or stable disease (SD) on prior anti-PD-1/L1 treatment, and no prior immunotherapy-related Grade ≥3 toxicities leading to treatment discontinuation. In FE mono and FE + PE 200 mg combo ECs, pts were randomized to FE 0.3 or 1 mg/kg; treatment was given every 3 wks up to 35 cycles until disease progression or unacceptable toxicity. Safety and efficacy were assessed. Biomarkers in tumor biopsies were analyzed.

Results: By 30 Mar 2020, 39 pts in the mono EC were evaluable (21 pts at 0.3; 18 pts at 1 mg/kg FE); all pts were anti-PD-1/L1 exp; 21/39 (54%) were anti-CTLA-4 exp; 7/39 (18%) had ≥4 prior lines of therapy. Of the 39 pts, 29 (74%) discontinued treatment due to progression. Response rate was 10% (4/39; 1 complete response, 3 partial responses); 8/39 (21%) pts had SD and 2/8 (25%) pts with SD had tumor size reductions (RECIST v1.1) at ≥19%; 5 pts (13%) had SD at ≥18 wks. Duration of response (DoR) was 2.0+ to 6.3 mo. BRAF and NRAS status did not impact clinical activity. Anti-CTLA-4 exp pts had a numerically higher response rate than anti-CTLA-4 naïve pts.

In the combo EC, 17 anti-PD-1/L1 exp pts were evaluable (6 pts at 0.3; 11 pts at 1 mg/kg FE); 12/17 (71%) were anti-CTLA-4 exp; 15/17 (88%) discontinued treatment, all due to progression. Response rate was 18% (3/17), DoR was 7.9+ to 8.2 mo, and disease control rate (response or SD) was 53% (9/17); 1 pt with SD had tumor size reduction of 10%.

Ongoing analyses with mono EC showed a 28.6% (2/7) response rate, DoR of 2.0+ to 6.3 mo, and mOS of ~26 mo in pts with ICOS high tumor-infiltrating T cells.

Sample size limits comparison; however, clinical activity was similar between FE doses and between BRAF+ and BRAF− pts. Adverse events (AEs) were consistent with AEs reported for PE.

Conclusions: FE is the first ICOS agonist with reported single-agent activity in ICB exp R/R melanoma, supporting ICOS as a target. FE + PE in combo shows promising clinical activity and manageable safety in R/R melanoma. Continued survival follow-up of ECs is warranted. Updated efficacy and PK/PD data to be presented.

Funding: Study 204691 (NCT02723955) funded by GSK in collaboration with Merck Sharp & Dohme Corp, a subsidiary of Merck & Co, Inc, Kenilworth, NJ, USA.

Citation Format: Michele Maio, Jeffrey S. Weber, Maria Vieito Villar, Frans L. Opdam, Victor Moreno, Omid Hamid, José Trigo, Michael Chisamore, Marco Balas, Sapna Yadavilli, David C. Turner, Courtney Henry, Xiao Ji, Catherine Ellis, Marc Ballas, Axel Hoos, Antoine Italiano. Inducible T cell costimulatory (ICOS) receptor agonist, feladilimab (FE), alone and in combination (combo) with pembrolizumab (PE): Results from INDUCE-1 relapsed/refractory (R/R) melanoma expansion cohorts (EC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr CT033.

Abstract CT150: A first-in-human phase I study of the OX40 agonist GSK3174998 (GSK998) +/- pembrolizumab in patients (Pts) with selected advanced solid tumors (ENGAGE-1)

Background: OX40 is a costimulatory receptor transiently expressed on the surface of activated T cells and some innate immune cells (e.g. NK cells). OX40 agonists have been shown to increase antitumor immunity and improve tumor-free survival in preclinical models, demonstrating increased efficacy when given in combination with a PD-1 inhibitor. GSK998 is a humanized IgG1 agonistic OX40 monoclonal antibody. Methods: ENGAGE-1 (NCT02528357) is a Phase 1 dose escalation study evaluating safety, PK, PD, and clinical activity of GSK998 (0.003-10 mg/kg IV Q3W) alone (Part 1) and in combination with pembrolizumab 200 mg IV Q3W (Part 2) in pts with previously treated advanced solid tumors: non-small cell lung cancer (NSCLC), squamous cell carcinoma of the head and neck, renal cell carcinoma, melanoma (MEL), bladder cancer, soft tissue sarcoma (STS), triple-negative breast cancer, and MSI-high colorectal carcinoma. Dose escalation used a continuous reassessment method and 4-week DLT period. Results: A total of 138 pts were enrolled (45 Part 1, 96 Part 2; 3 crossed over from Part 1). Two DLTs occurred in Part 2 only (G3 non-malignant pleural effusion 0.03 mg/kg; G1 myocarditis 10 mg/kg); MTD was not established. Most common (≥10%) treatment-related AEs (mostly G1-2) were diarrhea, fatigue (Part 1) and fatigue, nausea (Part 2). GSK998 demonstrated target engagement in the periphery as evidenced by PK and receptor occupancy (RO); a dose of 0.3 mg/kg was the threshold for linear PK & peripheral RO saturation over the 3-wk dose interval and was selected for further clinical evaluation in MEL, STS, and NSCLC in Part 2 expansion. Clinical responses and SD ≥24 weeks were observed in both PD-1/L1 naïve and experienced pts: Part 1 (1 PR, 1 SD; both 0.3 mg/kg) and Part 2 (2 CR, 7 PR, 9 SD; 0.01-3 mg/kg); Part 2 clinical responses were not correlated with baseline tumor PD-L1 expression levels; including one MEL pt with PD-L1 TPS=0 who progressed on prior CTLA-4/PD-1 treatment and had a CR (>18mo). Overall, peripheral and tumor expression of OX40 was low (<2% total cells in tumor were OX40 +ve). MultiOmyxTM data from tumor biopsies suggested increased NK/decreased Treg involvement in some responders. Conclusions: GSK998 +/- pembrolizumab was well tolerated, with evidence of target engagement; monotherapy clinical activity was limited. While combination responses may not be significantly greater than expected for pembrolizumab alone, responses were observed in some PD-1/L1 experienced pts and some with low PD-L1 expression. Given the low OX40 expression observed and preclinical evidence that increased expression improves activity of OX40 agonism, ongoing clinical evaluation of GSK998 will assess whether concurrent immune-stimulation or immunogenic cell death impacts OX40 expression and increases the efficacy of this agent. Combinations with TLR4 and ICOS agonists and an anti-BCMA antibody-drug conjugate are ongoing.

Citation Format: Sophie Postel-Vinay, Vincent K. Lam, Willeke Ros, Todd M. Bauer, Aaron R. Hansen, Daniel C. Cho, F. Stephen Hodi, Jan H.M. Schellens, Jennifer K. Litton, Sandrine Aspeslagh, Karen A. Autio, Frans L. Opdam, Meredith McKean, Neeta Somaiah, Stephane Champiat, Mehmet Altan, Anna Spreafico, Osama Rahma, Elaine M. Paul, Christoph M. Ahlers, Helen Zhou, Herbert Struemper, Shelby A. Gorman, Maura Watmuff, Kaitlin M. Yablonski, Niranjan Yanamandra, Michael J. Chisamore, Emmett V. Schmidt, Axel Hoos, Aurélien Marabelle, Jeffrey S. Weber, John V. Heymach. A first-in-human phase I study of the OX40 agonist GSK3174998 (GSK998) +/- pembrolizumab in patients (Pts) with selected advanced solid tumors (ENGAGE-1) [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr CT150.

Phase I study of lapatinib plus trametinib in patients with KRAS-mutant colorectal, non-small cell lung, and pancreatic cancer

PURPOSE

KRAS oncogene mutations cause sustained signaling through the MAPK pathway. Concurrent inhibition of MEK, EGFR, and HER2 resulted in complete inhibition of tumor growth in KRAS-mutant (KRASm) and PIK3CA wild-type tumors, in vitro and in vivo. In this phase I study, patients with advanced KRASm and PIK3CA wild-type colorectal cancer (CRC), non-small cell lung cancer (NSCLC), and pancreatic cancer, were treated with combined lapatinib and trametinib to assess the recommended phase 2 regimen (RP2R).

METHODS

Patients received escalating doses of continuous or intermittent once daily (QD) orally administered lapatinib and trametinib, starting at 750 mg and 1 mg continuously, respectively.

RESULTS

Thirty-four patients (16 CRC, 15 NSCLC, three pancreatic cancers) were enrolled across six dose levels and eight patients experienced dose-limiting toxicities, including grade 3 diarrhea (n = 2), rash (n = 2), nausea (n = 1), multiple grade 2 toxicities (n = 1), and aspartate aminotransferase elevation (n = 1), resulting in the inability to receive 75% of planned doses (n = 2) or treatment delay (n = 2). The RP2R with continuous dosing was 750 mg lapatinib QD plus 1 mg trametinib QD and with intermittent dosing 750 mg lapatinib QD and trametinib 1.5 mg QD 5 days on/2 days off. Regression of target lesions was seen in 6 of the 24 patients evaluable for response, with one confirmed partial response in NSCLC. Pharmacokinetic results were as expected.

CONCLUSION

Lapatinib and trametinib could be combined in an intermittent dosing schedule in patients with manageable toxicity. Preliminary signs of anti-tumor activity in NSCLC have been observed and pharmacodynamic target engagement was demonstrated.

Phase 1 study of the pan-HER inhibitor dacomitinib plus the MEK1/2 inhibitor PD-0325901 in patients with KRAS-mutation-positive colorectal, non-small-cell lung and pancreatic cancer

Background

Mutations in KRAS result in a constitutively activated MAPK pathway. In KRAS-mutant tumours existing treatment options, e.g. MEK inhibition, have limited efficacy due to resistance through feedback activation of epidermal growth factor receptors (HER).

Methods

In this Phase 1 study, the pan-HER inhibitor dacomitinib was combined with the MEK1/2 inhibitor PD-0325901 in patients with KRAS-mutant colorectal, pancreatic and non-small-cell lung cancer (NSCLC). Patients received escalating oral doses of once daily dacomitinib and twice daily PD-0325901 to determine the recommended Phase 2 dose (RP2D). (Clinicaltrials.gov: NCT02039336).

Results

Eight out of 41 evaluable patients (27 colorectal cancer, 11 NSCLC and 3 pancreatic cancer) among 8 dose levels experienced dose-limiting toxicities. The RP2D with continuous dacomitinib dosing was 15 mg of dacomitinib plus 6 mg of PD-0325901 (21 days on/7 days off), but major toxicity, including rash (85%), diarrhoea (88%) and nausea (63%), precluded long-term treatment. Therefore, other intermittent schedules were explored, which only slightly improved toxicity. Tumour regression was seen in eight patients with the longest treatment duration (median 102 days) in NSCLC.

Conclusions

Although preliminary signs of antitumour activity in NSCLC were seen, we do not recommend further exploration of this combination in KRAS-mutant patients due to its negative safety profile.

Feasibility and effectiveness of trifluridine/tipiracil in metastatic colorectal cancer: real-life data from The Netherlands

Background

The RECOURSE trial showed clinical efficacy for trifluridine/tipiracil for refractory metastatic colorectal cancer patients. We assessed the feasibility and effectiveness of trifluridine/tipiracil in daily clinical practice in The Netherlands.

Methods

Medical records of patients from 17 centers treated in the trifluridine/tipiracil compassionate use program were reviewed and checked for RECOURSE eligibility criteria. Baseline characteristics, safety, and survival times were compared, and prespecified baseline characteristics were tested in multivariate analyses for prognostic significance on overall survival (OS).

Results

A total of 136 patients with a median age of 62 years were analyzed. Forty-three patients (32%) did not meet the RECOURSE eligibility criteria for not having received all prior standard treatments (n = 35, 26%) and/or ECOG performance status (PS) 2 (n = 12, 9%). The most common grade ≥3 toxicities were neutropenia (n = 44, 32%), leukopenia (n = 8, 6%), anemia (n = 7, 5%), and fatigue (n = 7, 5%). Median progression-free survival (PFS) and median OS were 2.1 (95% CI, 1.8–2.3) and 5.4 months (95% CI, 4.0–6.9), respectively. Patients with ECOG PS 2 had a worse median OS (3.2 months) compared to patients with ECOG PS 0–1 (5.9 months). ECOG PS, KRAS-mutation status, white blood cell count, serum lactate dehydrogenase, and alkaline phosphatase were prognostic factors for OS.

Conclusions

Our data show that treatment with trifluridine/tipiracil in daily clinical practice is feasible and safe. Differences in patient characteristics between our population and the RECOURSE study population should be taken into account in the interpretation of survival data. Our results argue against the use of trifluridine/tipiracil in patients with ECOG PS 2.

Funding

Johannes J.M. Kwakman received an unrestricted research grant from Servier.

DPYD genotype-guided dose individualization to improve patient safety of fluoropyrimidine therapy: call for a drug label update

The fluoropyrimidine anticancer drugs, especially 5-fluorouracil (5-FU) and capecitabine, are frequently prescribed for several types of cancer, including breast, colorectal, head and neck and gastric cancer. In the current drug labels of 5-FU and capecitabine in the European Union and the United States, no adaptive dosing strategies are incorporated for polymorphic metabolism of 5-FU. Although treatment with fluoropyrimidines is generally well tolerated, a major clinical limitation is that a proportion of the treated population experiences severe, sometimes life-threatening, fluoropyrimidine-related toxicity. This toxicity is strongly affected by interindividual variability in activity of dihydropyrimidine dehydrogenase (DPD), the main metabolic enzyme for inactivation of fluoropyrimidines, with an estimated 3%-8% of the population being partially DPD deficient. A reduced functional or abrogated DPD enzyme is often caused by genetic polymorphisms in DPYD, the gene encoding for DPD, and heterozygous carriers of such DPYD polymorphisms have a partial DPD deficiency. When these partially DPD deficient patients are treated with a full dose of fluoropyrimidines, they are generally exposed to toxic levels of 5-FU and its metabolites, and the risk of developing severe treatment-related toxicity is therefore significantly increased.Currently, functional and clinical validity is well established for four DPYD variants (DPYD*2A, c.2846A>T, c.1679T>G and c.1236G>A), as those variants have retrospectively and in a large population study prospectively been shown to be associated with increased risk of fluoropyrimidine-associated toxicity. Patient safety of fluoropyrimidine treatment can be significantly improved by pre-emptive screening for DPYD genotype variants and dose reductions in heterozygous DPYD variant allele carriers, thereby normalizing 5-FU exposure. Based on the critical appraisal of currently available data, adjusting the labels of capecitabine and 5-FU by including recommendations on pre-emptive screening for DPYD variants and DPYD genotype-guided dose adjustments should be the new standard of care.

TAS-102 for Treatment of Advanced Colorectal Cancers That Are No Longer Responding to Other Therapies

TAS-102 is a novel oral formulation of trifluridine (TFT) and tipiracil hydrochloride (TPI), a thymidine phosphorylase inhibitor. TFT was originally synthesized in the 1960s and is a nucleoside analogue that impedes DNA synthesis by inhibition of thymidylate synthase. TFT's main mechanism of action, however, seems to be its incorporation into DNA, which distinguishes TFT from current well-known antimetabolites like 5-fluorouracil (5-FU). The rapid degradation of TFT brought initial clinical development to a halt, but TFT reentered clinical trials when addition of a TPI was found to improve the bioavailability of TFT. The combined TFT-TPI formulation was tested in patients with treatment-refractory metastatic colorectal cancer in the randomized phase III RECOURSE study. Compared with placebo, TAS-102 was associated with an overall survival (OS) and progression-free survival (PFS) benefit and a 32% reduction in risk of death [median OS, 7.1 (95% CI, 6.5-7.8) vs. 5.3 months (95% CI, 4.6-6.0); median PFS, 2.0 (95% CI, 1.9-2.1) vs. 1.7 months (95% CI, 1.7-1.8); HR for death, 0.68 (95% CI, 0.58-0.81, P < 0.001)]. Based on the results of this pivotal trial and supported by results from an earlier phase II study, TAS-102 recently gained FDA approval. This article reviews the development of TAS-102 and its therapeutic value for the proposed indication. Clin Cancer Res; 22(12); 2835-9. ©2016 AACR.

CYP2D6 Metabolism in Frail Elderly Compared to Non-Frail Elderly: A Pilot Feasibility Study

BACKGROUND

Frailty is a clinical phenotype that is associated with adverse health outcomes. Since frail patients may be more prone for adverse drug events and about 15-20 % of commonly prescribed drugs are metabolized by CYP2D6, we hypothesized that CYP2D6 metabolism is decreased in frail patients compared with healthy subjects.

METHODS

The (13)C-dextromethorphan breath test (DM-BT) was used to determine CYP2D6 phenotype using (13)C-dextromethorphan ((13)C-DM) as a probe. Eleven frail and 22 non-frail (according to the Fried criteria) subjects aged 70-85 years were phenotyped for CYP2D6.

RESULTS

Despite inequalities in CYP2D6 genotype between frail and non-frail subjects, the CYP2D6 gene activity score was equally distributed between the two groups (1.33 ± 0.50 vs. 1.28 ± 0.752). In male patients, no difference in total and free serum testosterone levels was observed between frail and non-frail men. Serum dehydroepiandrostenedione sulfate (DHEAS) levels were lower in frail subjects (1.56 μmol/L) compared with non-frail subjects (2.36 μmol/L), but the difference was not significant (p = 0.15). Body mass index was significantly correlated to CYP2D6 phenotype, whereas frailty score and individual parameters of frailty, Karnofsky score, and activities of daily living score were not significantly correlated to CYP2D6 phenotype. Although there was no difference in CYP2D6 phenotype observed between frail mean ± standard deviation (mean ± SD) area under the curve for delta over baseline values (0-2 h) (AUCDOB2h) 319 ± 169 ‰ min] and non-frail subjects (mean ± SD AUCDOB2h 298 ± 159 ‰ min), the present sample size is considered too small to draw any firm conclusions regarding a potential phenoconversion of CYP2D6 in frail elderly as compared with healthy subjects.

CONCLUSION

Frail and non-frail subjects did not differ in CYP2D6 phenotype, taking into account that the precalculated sample size was not achieved. Further studies with more patients are needed in order to adequately understand a possible correlation.

[Recurrent upper respiratory tract infections during and after rituximab therapy]

Rituximab maintenance therapy is indicated for the treatment of patients with non-Hodgkin's lymphoma (NHL) who responded to induction therapy. More than 10% of patients will develop rituximab-induced upper respiratory tract infections (URTIs). These infections are usually mild in patients receiving first-line or second-line treatment. Heavily pretreated patients sometimes undergo additional rituximab maintenance therapy. We describe three female patients aged 53, 43 and 42 years who were successfully treated with rituximab maintenance therapy after chemotherapy for three or more recurrences of NHL. These patients developed more serious recurrent URTIs due to rituximab-induced long-term hypogammaglobulinaemia. In one patient, serum IgG levels continued to decline for four years after rituximab therapy. Long-term immunoglobulin substitution was needed to treat these patients. Physicians should be aware that URTIs may develop in heavily pretreated patients even years after rituximab maintenance therapy and substitution with immunoglobulin may be warranted.

[Hyperglycaemia during treatment with everolimus]

BACKGROUND

Everolimus is an orally administered anti-cancer drug that inhibits the mammalian target of rapamycin (mTOR) signal transduction route. Use of everolimus may be associated with insulin resistance, manifesting in impaired glucose tolerance or hyperglycaemia.

CASE DESCRIPTION

A 74-year-old female patient with a locally recurrent breast cancer developed hyperglycaemia, which started 2 weeks after the initiation of treatment with everolimus 10 mg once daily. Metformin and insulin were administered to restore normoglycaemia.

CONCLUSION

At the initiation of treatment with an mTOR inhibitor such as everolimus the treating physician should be aware of the occurrence of hyperglycaemia. Metformin is then the medicine of first choice.

Lapatinib for advanced or metastatic breast cancer

Lapatinib is a potent reversible and selective inhibitor of the tyrosine kinase domains of epidermal growth factor receptor and human epidermal growth factor receptor (HER)-2 that exerts its action by competitive binding to the intracellular ATP-binding site of the receptor. It is registered for the treatment of advanced or metastatic HER-2+ breast cancer in combination with capecitabine and for hormone receptor-positive breast cancer in combination with an aromatase inhibitor. Lapatinib administered orally once daily is moderately to well tolerated, with rash and gastrointestinal adverse events as the main toxicities. In studies on the efficacy of lapatinib, direct comparisons between lapatinib and trastuzumab are lacking. Results of ongoing randomized phase III studies with lapatinib or trastuzumab in combination with taxanes as first-line agents for metastatic breast cancer as well as in the neoadjuvant and adjuvant settings are awaited.

The tolerability and efficacy of low-dose simvastatin in statin-intolerant patients

BACKGROUND/AIM

Statin intolerance is increasingly recognized as a therapy limiting factor in the primary and secondary prevention of cardiovascular disease. Since vulnerability to dose related adverse events differ between subjects treated with statins we hypothesized low-dose simvastatin would be tolerated and effective in statin-intolerant patients.

METHOD

A single center open label prospective observational study was performed assessing tolerability and efficacy of low-dose simvastatin treatment in 35 statin-intolerant patients. Statin intolerance was defined as not being able to tolerate a registered dose statin due to myalgia-myopathy, myositis, or elevation of serum liver enzyme levels. These statin-intolerant patients were treated with simvastatin with an initial dose of 2.5mg every other day. The dose was titrated upwards if possible. Tolerability was defined as remaining on treatment. Efficacy was defined as change of LDL-cholesterol compared to baseline.

RESULTS

The reached simvastatin dose ranged from 0.825 to 8.75mg/day with a mean dose of 4mg/day. Fifty-seven percent of the patients tolerated low-dose therapy and remained on treatment. Of these patients, 30% noted recurrent myalgia. Low-dose simvastatin significantly decreased mean(SD) LDL-cholesterol levels with 25.9(12.1)% (p<0.001). Eleven percent of the patients reached LDL-cholesterol target levels (<2.6mmol/l) in an intention to treat analysis and in 20% of patients that tolerated low-dose simvastatin.

CONCLUSION

Low-dose simvastatin therapy is tolerated in a considerable proportion of statin-intolerant patients with significant lipid lowering efficacy. Low-dose statin therapy can be considered in multidrug regimens in statin-intolerant patients.

Molecular characterization of 3-phosphoglycerate dehydrogenase deficiency--a neurometabolic disorder associated with reduced L-serine biosynthesis

3-phosphoglycerate dehydrogenase (PHGDH) deficiency is a disorder of L-serine biosynthesis that is characterized by congenital microcephaly, psychomotor retardation, and seizures. To investigate the molecular basis for this disorder, the PHGDH mRNA sequence was characterized, and six patients from four families were analyzed for sequence variations. Five patients from three different families were homozygous for a single nucleotide substitution predicted to change valine at position 490 to methionine. The sixth patient was homozygous for a valine to methionine substitution at position 425; both mutations are located in the carboxyterminal part of PHGDH. In vitro expression of these mutant proteins resulted in significant reduction of PHGDH enzyme activities. RNA-blot analysis indicated abundant expression of PHGDH in adult and fetal brain tissue. Taken together with the severe neurological impairment in our patients, the data presented in this paper suggest an important role for PHGDH activity and L-serine biosynthesis in the metabolism, development, and function of the central nervous system.