BLU-945, a highly potent and selective 4th-generation EGFR ...

BLU-945, a highly potent and selective 4th-generation EGFR TKI for the treatment of EGFR+/T790M/C797S resistant NSCLC

Stefanie Schalm1, Tom Dineen1, Sun Min Lim2, Chae-Won Park2, John Hsieh1, Rich Woessner1, Zhuo Zhang1, Kevin Wilson1, Meredith Eno1, Doug Wilson1, Brett Williams1, John Campbell1, Chris De Savi1, Faith Stevison1, Caitlin Utt1, Timothy Guzi1, Marion Dorsch1, Klaus Hoeflich1, Byoung Chul Cho2

1Blueprint Medicines Corporation, Cambridge, Massachusetts, USA; 2Yonsei Cancer Center, Yonsei University College of Medicine, Seoul, South Korea

1296P

Background

? Osimertinib, a 3rd-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI), has favorably impacted the treatment of patients with EGFR-driven non-small cell lung cancer (NSCLC) and extended overall survival compared with older EGFR TKIs, including the 1st-generation agent gefitinib1

? The C797S mutation is the most frequent on-target resistance mechanism to osimertinib and there are no targeted therapies approved for patients with disease progression2

? We are developing targeted agents to treat C797S-driven resistance with the goal of improving patient outcomes and prolonging clinical benefit ? BLU-945 (Figure 1) is a 4th-generation EGFR TKI designed to target the EGFR+(L858R or ex19del)/T790M/C797S triple mutant following treatment with a 1st-line 1st-generation EGFR TKI and 2nd-line osimertinib3,4 ? A second 4th-generation EGFR TKI aims to target the EGFR+/C797S double mutant following treatment with 1st-line osimertinib3

? Here we describe preclinical data for BLU-945 supporting initiation of clinical development in EGFR-driven NSCLC

Figure 1: Rationale for the development of BLU-945 targeting EGFR+/T790M/C797S

T790M

C797S

1st-generation

EGFR TKI C797S

Osimertinib

Osimertinib

T790M

Blueprint EGFR+ C797S

BLU-945

T790M

Methods

C797S

? BLU-945 activity on EGFR mutants and EGFR wild-type (WT) was tested in biochemical assays and cellular phosphorylation-specific EGFR AlphaLisa assays

? The in vivo antitumor activity of BLU-945 was evaluated in an NCI-H1975 cell line-derived tumor xenograft (CDX) model, as well as in osimertinib-resistant CDX-derived and patient-derived xenograft (PDX) models of NSCLC

Results

BLU-945 is a highly potent and selective EGFR+ T790M/C797S inhibitor

? Highly potent inhibitor of EGFR+/T790M/C797S and EGFR+/T790M resistant mutants ? Excellent EGFR WT and overall kinome selectivity ? BLU-945 only inhibits 1% of the kinome >90% at a concentration of 3 ?M ? Selectivity profile enables combinations to cover wide spectrum of resistant mechanisms

Table 1: BLU-945 is a subnanomolar EGFR+/T790M/C797S and EGFR+/T790M inhibitor with >900-fold selectivity over EGFR WT

Compound

Enzyme activities IC50 (nM) at 1 mM ATP with enzyme-inhibitor pre-incubation

L8585R

L858R/

L858R/

ex19del ex19del/

ex19del/ EGFR WT

T790M T790M/C797S (746?750) T790M T790M/C797S

BLU-945

7.1

0.4

0.5

71.4

0.8

0.8

736.3

Erlotinib

0.3

3132.7

5654.7

0.2

1394.7

1906.6

9.8

Gefitinib

0.1

1667.2

3921.8

0.1

632.7

1219.7

3.5

Osimertinib

0.9

0.6

5461.6

0.8

0.6

649.9

1.6

ATP, adenosine triphosphate; IC50, half maximal inhibitory concentration.

Mean tumor volume (mm3) ? SEM Mean tumor volume (mm3) ? SEM Mean tumor volume (mm3) ? SEM Mean tumor volume (mm3) ? SEM

0 10 100 300 1000 1 10 100 300 0 10 100 300 1000 1 10 100 300

Mean tumor volume (mm3) ? SEM

BLU-945 inhibits EGFR+/T790M/C797S driven pathway activation

Table 2: BLU-945 potently inhibits EGFR+/T790M/C797S and EGFR+/T790M autophosphorylation

Cellular pEGFR inhibition IC50 (nM)

Cell lines

Engineered Ba/F3 cell lines

NCI-H1975 Compound (L8585R/T790M)

PC-9 (ex19del)

A431 (EGFR WT)

L858R

L858R/

ex19del/

T790M/C797S T790M/C797S

BLU-945

1.2

129.5

544.4

21.5

2.9

4.4

Erlotinib

>10,000

3.9

140.6

5.9

6655.5

4524.8

Gefitinib

4679.8

1.8

16.5

4.6

6707.7

4864.7

Osimertinib

4.7

2.1

115.9

11.0

7754.6

>10,000

Figure 2: BLU-945, but not osimertinib, inhibits the EGFR pathway in (A) ex19del/T790M/C797S and (B) L858R/T790M/C797S driven Ba/F3 cell lines

A. Osimertinib BLU-945 Drug concentration (nM) pEGFR (Y1068) EGFR pAKT (S473) AKT pERK ERK pS6 S6 GAPDH Ba/F3 ex19del/T790M/C797S

B. Osimertinib BLU-945

Drug concentration (nM) pEGFR (Y1068)

6 hrs

EGFR

pAKT (S473)

AKT

pERK

ERK

pS6

S6 GAPDH

Ba/F3 L858R/T790M/C797S

BLU-945 has antitumor activity on EGFR+/T790M and EGFR+/T790M/C797S driven cancers

Figure 3: Oral administration of BLU-945 showed significant tumor regression in (A) NCI-H1975 NSCLC CDX (L858R/T790M) tumor model similar to covalent drug osimertinib and (B) an osimertinib resistant Ba/F3 CDX (ex19del/T790M/C797S) model; (C) PD analysis for 3A

A.

1000 NCI-H1975 (L858R/T790M)

B. 1000 Ba/F3 ex19del/T790M/C797S

750

750

Vehicle, BID

BLU-945, 30 mg/kg BID

BLU-945, 150 mg/kg QD

500

500

BLU-945, 100 mg/kg BID

Osimertinib, 25 mg/kg QD

250

250

0

0

5

10

15

Days post treatment initiation

0

0

5

10

15

Days post treatment initiation

C.

Vehicle

BLU-945, 30 mg/kg BIDa

Vehicle

2 h

2 h

6 h

12 h

6 h

Vehicle 2 h

p-EGFR p-ERK

GAPDH

p-EGFR p-ERK

GAPDH

BID, twice daily; PD, pharmacodynamic; QD, once daily; SEM, standard error of the mean. aDosed for 3 days.

BLU-945,100 mg/kg BIDa

2 h

6 h

12 h

Vehicle 6 h

Figure 4: In an (A) osimertinib-resistant EFGR ex19del/T790M/C797S patient-derived cell line xenograft (PDCX) model, (B) oral administration of BLU-945 led to significant tumor regression

A.

PDC

B.

Gefitinib Osimertinib

del19 del19/T790M

ex19del/T790M/C797S

500

450

0

1

2

3

4

5

400

Years

350

YU-1097 (ex19del/T790M/C797S)

Vehicle BID (n=6) Osimertinib, 25mg/kg QD (n=7) BLU-945, 100mg/kg BID (n=6)

T790M (p14)

C797S (p14)

300

250

*

*

200

150

ACG ATG

TGC TCC

100

? PDCX model developed from patient who progressed on gefitinib and osimertinib

? RNA sequencing (RNA-seq) analysis of PDX model suggests EGFR amplification and allelic heterogeneity

50

0 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 Days post treatment initiation

? Oral administration of BLU-945 (100 mg/kg BID) was sufficient for tumor regression in this PDCX model

? BLU-945 was well tolerated in the PDCX animal model

BLU-945 combination with 1st-and 3rd-generation EGFR TKIs resulted in further improved tumor regression compared with BLU-945 alone

Figure 5: BLU-945 showed significant tumor regression in combination with osimertinib (A) or (B) gefitinib, in a NSCLC PDX (ex19del/T790M/C797S) model with EGFR amplification and allelic heterogeneity

? PDX (ex19del/T790M/C797S) model developed from patient with NSCLC (poorly-moderately differentiated adenocarcinoma) who progressed through >5 lines of therapy, including chemotherapy, icotinib, erlotinib, and osimertinib

? RNA-seq analysis of PDX model suggested EGFR amplification and allelic heterogeneity

A.

LUPF104 (ex19del/T790M/C797S)

BLU-945 + osimertinib

1500

B.

LUPF104 (ex19del/T790M/C797S)

BLU-945 + gefitinib

1500

1250 1000

750 500

1250 1000

750 500

Vehicle BLU-945, 100 mg/kg BID Osimertinib, 25 mg/kg QD Gefitinib, 18.75 mg/kg QD BLU-945 100 mg/kg + osimertinib 5 mg/kg BLU-945 100 mg/kg + gefitinib 18.75 mg/kg

250

250

0

0

10 20 30 40 50

Days post treatment initiation

0

0

10 20 30 40 50

Days post treatment initiation

? Single agent BLU-945 was sufficient for tumor stasis in this model ? Co-dosing BLU-945 with either osimertinib or gefitinib led to significant tumor regression ? Single agent and combination doses were well tolerated in the animal model ? Data suggest that BLU-945 can be combined with other EGFR TKIs to address

allelic EGFR heterogeneity

BLU-945 demonstrates intracranial activity when administered orally

Figure 6: Oral administration of BLU-945 100 mg/kg resulted in intracranial activity in a NCI-H1975 L858R/T790M-luc intracranial model

Vehicle, BID

1750

BLU-945, 100 mg/kg BID

1750

Osimertinib, 25 mg/kg QD

1750

Bioluminescence photons/sec / 106 Bioluminescence photons/sec / 106 Bioluminescence photons/sec / 106

1500

1500

1500

1250

1250

1250

1000

1000

1000

750

750

750

500

500

500

250

250

250

0

0

5

10

15

Days post treatment initiation

0

0

5

10

15

Days post treatment initiation

0

0

5

10

15

Days post treatment initiation

Conclusions

? BLU-945 is a potentially best-in-class oral, selective, potent, 4th-generation EGFR TKI with activity against the EGFR+(L858R or ex19del)/T790M/C797S triple mutants

? In preclinical models, BLU-945 demonstrated potent, robust EGFR pathway inhibition and antitumor activity at well-tolerated doses in the NCI-H1975 CDX model and osimertinib-resistant CDX and PDX models of NSCLC

? Combination of BLU-945 with either 1st-generation (gefitinib) or 3rd-generation (osimertinib) EGFR TKI showed enhanced antitumor activity compared with single agent treatment in an EGFR+/T790M/C797S-driven PDX model, suggesting potential for monotherapy and/or combination therapy in the clinical setting

? BLU-945 demonstrated robust antitumor activity in an NCI-H1975 L858R/T790M-luc intracranial model

? Clinical development of BLU-945 monotherapy is expected to begin with an international phase 1 dose-escalation trial in patients with EGFR-driven NSCLC in the first half of 2021, and future clinical development of BLU-945 in combination with other TKIs across multiple treatment settings is planned

References

1. Ramalingam SS et al. N Engl J Med. 2020;382:41?50; 2. Lazzari C et al. J Thorac Dis. 2020;12:2851?2858; 3. Leonetti A et al. Br J Cancer. 2019;121:725?737; 4. Mok, TS et al. N Engl J Med. 2017;376:629?640.

Acknowledgments

Some of the cell assays and in vivo experiments were conducted at Pharmaron Beijing Co., Ltd (China), Shangai LIDE Biotech Co., Ltd (China), WuXi AppTec Co., Ltd (China). Medical writing support was provided by Cristina Tomas, PhD, and editorial support was provided by Michelle Seddon, Dip Biotech Co., Psych, all of Paragon, Knutsford, UK, supported by Blueprint Medicines Corporation, Cambridge, MA, according to Good Publication Practice guidelines.

Disclosures

Study sponsored by Blueprint Medicines Corporation. BW, CS, CU, DW, FS, JC, JH, KH, KW, MD, ME, RW, SS, TD, TG, and ZZ are employees of Blueprint Medicines Corporation, or were at the time the work presented was developed, and own stock. BCC received research funding from Abbvie, AstraZeneca, Bayer, Blueprint Medicines Corporation, Champions Oncology, Dizal Pharma, Dong-A ST, Eli Lilly, GIInnovation, Janssen, Medpacto, MOGAM Institute, MSD, Novartis, Ono, Yuhan; consulted for AstraZeneca, Blueprint Medicines Corporation, BMS, Boehringer-Ingelheim, Eli Lilly, Janssen, Medpacto, MSD, Novartis, Ono, Pfizer, Roche, Takeda, Yuhan; owns stock in Bridgebio therapeutics, Gencurix Inc, KANAPH Therapeutic Inc., TheraCanVac Inc.; participated in scientific advisory board for KANAPH Therapeutic Inc; reports royalties from Champions Oncology; and is the founder of Daan biotherapeutics. C-WP and SML and have no disclosures.

Presented at ESMO 2020, September 14?18, 2020, Virtual Format. Please contact medinfo@ for permission to reprint and/or distribute

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