For qualitative detection of actionable alterations in the FGFR3 gene
The therascreen FGFR RGQ RT-PCR Kit is a qualitative in vitro diagnostic test for the detection of two point mutations in exon 7 [p.R248C (c.742C>T), p.S249C (c.746C>G)], two point mutations in exon 10 [p.G370C (c.1108G>T) and p.Y373C (c.1118A>G)] and two fusions (FGFR3:TACC3v1 and FGFR3:TACC3v3) in the FGFR3 gene.
The therascreen FGFR RGQ RT-PCR Kit is the only FDA-approved companion diagnostic (CDx) test for the identification of patients with cases of urothelial cancer (UC) that harbor these actionable FGFR alterations, and for whom treatment with BALVERSA (erdafitinib) is indicated.
Concordance between the clinical trial assay (CTA) used to identify patients for recruitment to the Phase 2 clinical trial of BALVERSA (42756493-BLC2001) and the therascreen FGFR RGQ RT-PCR Kit (CDx) was evaluated in a bridging study (1).
Samples with valid results for both therascreen FGFR RGQ RT-PCR Kit and CTA (279/287 patients; 97.2%) were analyzed to assess the positive percent agreement (PPA), negative percent agreement (NPA) and overall percent agreement (OPA), based on agreement between the two methods for overall FGFR gene alteration status (i.e., FGFR Alteration Detected or FGFR Alteration Not Detected) Results are shown in Table 1.>
| Measure of agreement | Percent agreement, % (N) | Two-sided 95% CI |
| Positive percent agreement | 85.2% (69/81) | 75.9, 91.3 |
| Negative percent agreement* | 97.0% (192/198) | 93.5, 98.6 |
| Overall percent agreement | 93.5% (261/279) | 90.0, 96.1 |
* Prior chemotherapy information was not collected for CTA-negative patients. Therefore, 198 CTA-negative subjects included both chemo-relapsed/chemo-refractory patients and chemo-naïve patients.
The primary objective of the BLC2001 clinical trial was to evaluate the objective response rate (ORR) to treatment with BALVERSA in subjects with cases of UC in which FGFR alterations were detected. ORR was defined as complete response (CR) plus partial response (PR) by RECIST criteria, as assessed by blinded independent review committee (BIRC). The observed clinical benefit of treatment with BALVERSA in the subset of patients in which FGFR alterations were detected with both the therascreen FGFR RGQ RT-PCR Kit and the CTA (n = 69) was comparable to that observed in the full study population, as defined by the CTA only (n = 87). The ORR in patients in whom FGFR alterations were detected by both the therascreen FGFR RGQ RT-PCR Kit and the CTA, as assessed by BIRC, was 33.3% (95% CI: 23.4-45.1%).
The therascreen FGFR RGQ RT-PCR Kit is therefore indicated for use as an aid in identifying patients with cases of urothelial cancer which harbor these alterations and are therefore eligible for treatment with BALVERSA (erdafinitib).
The therascreen FGFR RGQ RT-PCR assay is based on the selective amplification of alterations in the FGFR genes using the Rotor-Gene Q MDx (US) instrument for sensitive and specific analysis. The assay exploits the qPCR oligonucleotide hydrolysis principle using TaqMan probes.
Allele-specific technology allows accurate and highly reproducible detection of alterations, based on the use of specific forward and reverse primers and probes; only a perfect match between the primers and probes with the target cDNA allows extension and amplification in the PCR reaction. Result reporting is fully automated. If both the run controls and the sample results are valid and sufficient assay target amplification occurs below the predetermined cycle number cutoff threshold, the report will show the FGFR alteration(s) detected in each sample.
The fast and simple workflow takes ~12 hours from Sample to Insight.
RNA is first prepared from formalin-fixed paraffin-embedded (FFPE) urothelial tumor samples using the RNeasy DSP FFPE Kit. Purified RNA is then reverse transcribed using Reverse Transcriptase to generate cDNA for real-time PCR analysis. Optimized ready-to-use reverse transcription reagents and PCR master mixes provided in the kit enable high-fidelity reverse transcription and sensitive real-time PCR on the Rotor-Gene Q MDx (US) instrument. Qualitative results are displayed in Rotor-Gene AssayManager software, informing the system operator if one or more of the four point mutations and two fusions in the FGFR3 gene detected by the kit are present.
The therascreen FGFR RGQ RT-PCR kit is also designed to identify FGFR2 fusions FGFR2:BICC1 and FGFR2:CASP7 and FGFR3 fusion FGFR3:BAIAP2L1, because patients harboring these FGFR fusions were eligible for the BLC2001 clinical trial. However, the test is not clinically validated to detect these three fusions. Drug safety and efficacy has not been established for cases of UC harboring these fusions and no claims are made for the use of the therascreen FGFR RGQ RT-PCR kit as an aid in the selection of such patients for treatment with BALVERSA (erdafitinib).
The therascreen FGFR RGQ RT-PCR Kit enables qualitative detection of four point mutations and two fusions of the FGFR3 gene for in vitro diagnostic use. It is the only FDA-approved CDx assay for the selection of patients with cases of urothelial cancer (UC) harboring actionable alterations, for whom treatment with BALVERSA (erdafitinib) is indicated.
1. Janssen Biotech, Inc. Data on file.
