SDX-7320, a Novel Inhibitor of Methionine Aminopeptidase 2

Poster #1068

SDX-7320, a novel inhibitor of methionine aminopeptidase 2 (MetAP2), inhibits MCF-7 tumor growth and mechanisms of resistance in combination with palbociclib (Ibrance®)

Peter Cornelius1, Benjamin Mayes1, Pierre Dufour1, Sara Little2, Andrew Slee2, Raphael Nir3, Adam Nir3, Bradley Carver1, James Shanahan1 1SynDevRx Inc., Cambridge, MA; 2NeoSome Life Sciences, Lexington, MA, 3SBH Sciences, Natick, MA.

The Metabo-Oncology Company™ SDX-7320: A Novel, Clinical-Stage Polymer-Drug Conjugate A methionine aminopeptidase 2 (MetAP2) inhibitor conjugated to a polymer backbone

▪ SDX-7320 is a pro-drug of a small molecule MetAP2 inhibitor (fumagillin-class) ▪ The prodrug is a polymer-drug conjugate and consists of: 1. A hydroxypropylmethacrylamide (HPMA) – methacrylamide (MA) co-polymer carrier 2. A specific peptide linker (enzyme-cleavable) 3. The pharmacologically active fumagillol derivative SDX-7539 Active drug ▪ Metabolism in vivo yields the pharmacologically active drug SDX-7539 SDX-7539 (MetAP2 inhibitor) (MetAP2 inhibitor) ▪ Polymer-conjugation: 1. limits CNS penetration of small molecule (prevents CNS toxicity seen with other MetAP2 inhibitors) 2. solubilizes the hydrophobic small molecule MetAP2 3. enzyme-mediated release minimizes small molecule concentrations in general circulation • Cell cycle arrest (increased p21, decreased CDK2, Cyclin E1, Rb in ER+ tumors) ▪ SDX-7320 has completed a Phase I trial, in late-stage, heavily- • Inhibits signaling downstream of WNt5a (blocks non-canonical wnt pathway) pretreated cancer patients with solid tumors • Decreases levels of pro-angiogenic growth factors (VEGF-C, bFGF) • Modifies immune-suppressive tumor immune micro-environment (↓Arg-1, ↓Treg) • Improves insulin sensitivity in states of insulin resistance • Impacts adipose tissue to decrease leptin, increase adiponectin in circulation

2 Study Design: SDX-7320 +/- CDK4/6 Inhibitor Palbociclib CDK4/6 inhibitors are standard-of-care in 1st line treatment for metastatic ER+/Her2- breast cancer

Objectives: 1. To evaluate the anti-tumor activity of SDX-7320 and the CDK4/6 inhibitor palbociclib alone and in combination in orthotopic MCF-7 xenografts. 2. To measure the changes in known and reported mechanisms of treatment resistance to CDK4/6 inhibitors.

Methods: ▪ Female nude mice (Charles River) were implanted with one 90-day (0.72 mg) β-estradiol pellet 3 days prior to cell inoculation. ▪ MCF-7 cells (5 x 106 in 1:1 PBS/Matrigel) were injected into the fourth mammary gland. ▪ Treatment with test agents began when group mean tumor volume was 125-175 mm3 with no tumors <100 mm3. ▪ Tumor volume and body weight were measured twice weekly; gross observations were made daily. ▪ At end of study, whole blood collected by cardiac puncture (under ether anesthesia) for CBC, tumors dissected (n=3): half of each tumor was placed in RNALater (for analysis of gene expression) and the other half was homogenized in RIPA buffer containing protease and phosphatase inhibitors then frozen at -70ºC.

Vehicle SDX-7320 Palbociclib Group N (QD to End of Study Starting Day 2) (Q4D to End of Study Starting Day 1) (QD to End of Study Starting Day 2)

Vehicle (PO: lactic acid buffer)) 10 X

SDX-7320 8 mg/kg (SC) 10 X

SDX-7320 8 mg/kg (SC) + Palbo 20 mg/kg (PO) 10 X X

SDX-7320 8 mg/kg (SC) + Palbo 40 mg/kg (PO) 10 X X Palbociclib 20 mg/kg (PO) 10 X Palbociclib 40 mg/kg (PO) 10 X

3 Anti-tumor Efficacy with SDX-7320 and Palbociclib Both SDX-7320 and palbociclib were efficacious alone; additional activity with combinations MCF-7 Tumor Volume (Day 25) ** * **** 2500 *** *

e 2000

)

u l

E 1500

r 3

o 1000

( u

T 500

*p < 0.05, **p < 0.01, ***p < 0.005, ****p < 0.001 versus Vehicle; One-way ANOVA with multiple comparisons

T T TGI (%) 0 t Significant inhibition of tumor growth both in response to Vehicle 129 1060 - SDX-7320 alone, and to palbociclib alone. SDX (8) 129 602 49 SDX (8) + 129 Additional efficacy was observed with the combination of Palbo (20) 406 70 SDX-7320 and palbociclib (20 and 40 mg/kg). SDX (8) + 129 Palbo (40) 313 80 Tumor growth in vehicle group was variable ▪ One animal removed from analysis due to poor tumor growth Palbo (20) 129 623 47 ▪ Tumor volume decreased after day 25 due to death of two mice with large Palbo (40) 129 451 65 tumors, therefore day 25 data was used for TGI% and statistical analysis

Source: SDX internal data 4 Survival Trend Favored SDX-7320 Plus Lower Dose Palbociclib Palbociclib at 40 mg/kg was poorly tolerated in this model

Palbociclib @40 mg/kg was not well tolerated, leading to multiple premature events.

Combination of SDX-7320 with palbociclib (40 mg/kg) improved survival compared to Palbociclib (40 mg/kg) alone.

Source: SDX internal data 5 Safety: Changes in Body Weight

SDX-7320 typically induces loss of fat mass in normal animals B o d y W e ig h t C h a n g e

V e h ic le 1 0

S D X - 7 3 2 0 (8 m g /k g ) + P a lb o ( 2 0 m g /k g )

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Body Weight t

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Body Weight Change

a y SDX-7320 (8 mg/kg) Palbo (40 mg/kg) h

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Vehicle % ( SDX-7320 (8 mg/kg) + Palbo (20 mg/kg) 10 B

SDX-7320 (8 mg/kg) )

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-2 0 0 1 0 2 0 3 0 4 0 No additional weight loss seen with combination. T im e (d a y s )

*p < 0.05, **p < 0.01 versus vehicle; multiple t-tests (Holm-Sidak method) Source: SDX internal data 6 Safety: Changes in Neutrophils – A Known Toxicity with Palbociclib* Lack of significant reduction in combination suggests potential for improved hematologic safety profile

N e u tro p h ils V e h ic le Adverse Event Summary (PALOMA-3)* (n = 3 ) S D X -7 3 2 0 (8 m g /k g ) 2 0 0 0 S D X - 7 3 2 0 ( 8 m g /k g ) + P a lb o ( 2 0 m g /k g )

S D X - 7 3 2 0 ( 8 m g /k g ) + P a lb o ( 4 0 m g /k g ) ) P a lb o ( 2 0 m g /k g )

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1 0 0 0

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Severe neutropenia is a major toxicity associated with palbociclib; reversed in combination of SDX-7320 and palbociclib (40 mg/kg).

*Cristofanelli, Lancet Oncol (2016), 17: 425-39; McAndrew et al., Br J Cancer 123, 912–918 (2020) 7 Exploring Resistance Mechanisms to CDK4/6 Inhibition Pathways implicated in resistance may be attenuated by MetAP2 inhibition

Potential mechanisms of CDK4/6 resistance: ▪ Cyclin E1 ▪ CDK 2 ▪ Akt signaling ▪ Autophagy ▪ Cancer stem cell initiation

Methods: To assess the effect of SDX-7320 alone and in combination with palbociclib, tumor tissues (n=3/group) were dissected, homogenized then frozen, later thawed and then analyzed using an automated Western blot device (WES/ProteinSimple). Key mechanisms implicated in the development of resistance to CDK4/6 inhibitors.

Source: Portman et al., Endocr Relat Cancer 2019 Jan;26(1):R15-R30 8 Cyclin E1: Lower Expression Associated with Improved Outcomes* High levels associated with resistance to palbociclib, lower gene expression mapped to longer PFS

Cyclin E1 Protein Vehicle Change in Cyclin E1 SDX-7320 (8 mg/kg) 0

125000 )

e l

SDX-7320 (8 mg/kg) + Palbo (20 mg/kg) c

100000 SDX-7320 (8 mg/kg) + Palbo (40 mg/kg) e

l o

Palbo (20 mg/kg) t

c -20

e l

75000 v a

Palbo (40 mg/kg) i

n l

50000 e e

g -40

a h

25000 h

C % 0 ( -60

Association of cell cycle pathway gene expression and the efficacy of palbociclib (PAL) in combination with fulvestrant (FUL).*

0.5 1.0 ←Favors Palbo+ Ful Favors PBO + Ful→

Source: SDX internal data *Turner et al., J Clin Oncol (2019) 37:1169-1178 9 CDK2 Associated w/Progression of Breast Cancer, Resistance to CDKi CDK2 protein decreased by SDX-7320 alone, further decrease w/combo

CDK2 Protein Vehicle Change in CDK2 **** SDX-7320 (8 mg/kg)

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SDX-7320 (8 mg/kg) + Palbo (40 mg/kg) e -20 K

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Palbo (40 mg/kg) v

40000 a

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20000 a C

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***p < 0.005, ****p < 0.001 versus SDX (8) + Palbo (40); *p < 0.05 versus SDX (8); one-way ANOVA with multiple comparisons one-way ANOVA with multiple comparisons

▪ Combination of palbociclib (40 mg/kg) and SDX-7320 significantly decreased the level of intra-tumoral CDK2 protein relative to both vehicle-treated controls and SDX-7320 alone

▪ The change in intra-tumoral CDK2 protein relative to vehicle was significantly greater in the combination of palbociclib (40 mg/kg) and SDX-7320 relative to SDX-7320 alone

Source: SDX internal data 10 Akt: Common Pathway of Drug Resistance for Many Drug Classes* Significant decreases with SDX-7320 monotherapy, and when combined with palbociclib (20, 40 mg/kg)

A k t P ro te in C h a n g e in A k t

* V e h ic le 0

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S D X - 7 3 2 0 (8 m g /k g ) + P a lb o ( 2 0 m g /k g ) h

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*p < 0 .0 5 v e r s u s V e h ic le ; o n e -w a y A N O V A w ith m u ltip le c o m p a ris o n s

Source: SDX internal data *Liu R, et al, Cell Death Dis. 2020;11(9):797. doi:10.1038/s41419-020-02998-6 11 Akt: Activation by Phosphorylation pAkt (S473) decreased by SDX-7320 and in combination with palbociclib at 40 mg/kg

P h o s p h o -A k t P ro te in C h a n g e in P h o s p h o -A k t

V e h ic le

S D X -7 3 2 0 (8 m g /k g ) 4 0

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S D X - 7 3 2 0 (8 m g /k g ) + P a lb o ( 2 0 m g /k g ) l

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1 0 0 0 0 c

% 0 ( -4 0

Source: SDX internal data 12 Rb: Reduced by Both Agents; Possible Additivity Tumors with lower Rb protein showed a trend towards better outcomes in post-hoc PALOMA-3 analysis*

Rb Protein

* Vehicle Change in Rb

* SDX-7320 (8 mg/kg) 0

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4000000 *** SDX-7320 (8 mg/kg) + Palbo (20 mg/kg) l

c i

** SDX-7320 (8 mg/kg) + Palbo (40 mg/kg) h

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Palbo (20 mg/kg) o

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Palbo (40 mg/kg) i -40

a t

n l

2000000 g

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-60

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1000000 a

h -80

% ( -100

*p < 0.05, **p < 0.01, ***p < 0.005, versus Vehicle; one-way ANOVA with multiple comparisons

Interestingly, Turner et al* reported that lower Rb expression trended towards better PFS.

0.5 1.0 ←Favors Palbo+ Ful Favors PBO + Ful→ Source: SDX internal data *Turner et al., J Clin Oncol (2019) 37:1169-1178 13 LC3B: Autophagy Marker; Induced by Palbociclib Palbociclib-induced LC3B was attenuated when palbociclib was combined with SDX-7320

LC3B Protein Change in LC3B *** Vehicle *** **** 150

SDX-7320 (8 mg/kg) ) **** e

* l c

SDX-7320 (8 mg/kg) + Palbo (20 mg/kg) i ** 150000 h

** e

SDX-7320 (8 mg/kg) + Palbo (40 mg/kg) B V

3 100

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Palbo (20 mg/kg) t

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a Palbo (40 mg/kg) i

100000 t

a 50

g r

g n 50000 h

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*p < 0.05, **p < 0.01, ***p < 0.005, ****p < 0.001 versus Palbo (40); **p < 0.01, ***p < 0.005, ****p < 0.001 versus Palbo 20 or Palbo 40; one-way ANOVA with multiple comparisons one-way ANOVA with multiple comparisons

“Cancer cells activate autophagy in response to palbociclib, and that blockade of autophagy significantly improves the efficacy of CDK4/6 inhibition in vitro and in vivo in cancers with an intact G1/S transition.”*

Source: SDX internal data *Vijayaraghavan, et al., Nat. Commun.8, 15916 doi: 10.1038/ncomms15916 (2017). 14 Summary and Next Steps

Summary ▪ SDX-7320 alone (8 mg/kg) inhibited MCF-7 tumor growth by 49% and palbociclib alone (20, 40 mg/kg) exhibited dose- dependent efficacy (47% and 65%, respectively). This analysis is based on day 25 tumor volume data.

▪ When SDX-7320 was combined with palbociclib (20, 40 mg/kg) additional inhibition of tumor growth was observed (70 and 80% respectively). This analysis is based on day 25 tumor volume data.

▪ Both palbociclib and SDX-7320 alone suppressed levels of neutrophils by 30-40% relative to vehicle-treated mice, while the combination of SDX-7320 and palbociclib (40 mg/kg) increased neutrophils 49% relative to vehicle-treated mice.

▪ The combination of SDX-7320 and palbociclib attenuated the expression of proteins associated with resistance to palbociclib (i.e., cyclin E1, CDK2, Akt, Rb and LC3B).

Next Steps ▪ Complete the analysis of gene expression data (RNASeq) ▪ Ongoing

▪ Develop palbociclib-resistant MCF-7 model ▪ Can SDX-7320 overcome acquired resistance to palbociclib?

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