ResTORbio : Corporate Presentation February 2019

Targeting the biology of aging to treat aging-related diseases

Corporate Presentation

February 2020

Forward-looking statements

This presentation has been prepared by resTORbio, Inc. ("we," "us," "our," "resTORbio," or the "Company") and is made for informational purposes only and does not constitute an offer to sell or a solicitation of an offer to buy securities. This presentation may contain "forward-looking statements" within the meaning of the Private Securities Litigation

Reform Act of 1995, including, but not limited to, statements regarding the safety, efficacy and regulatory and clinical progress of our product candidates, including RTB101 alone and in combination with a rapalog, such as everolimus or sirolimus. All such forward-looking statements are based on management's current expectations of future events and are subject to a number of risks and uncertainties that could cause actual results to differ materially and adversely from those set forth in or implied by such forward-looking statements. The use of words such as, but not limited to, "may," "might," "will," "should," "expect," "plan," "anticipate," "believe," "estimate," "project," "intend," "future," "potential," or "continue," and other similar words or expressions are intended to identify forward-looking statements. Forward-looking statements are neither historical facts nor assurances of future performance. Instead, they are based on our current beliefs, expectations and assumptions regarding the future of our business, future plans and strategies, our clinical results and other future conditions. All statements other than statements of historical facts contained in this presentation, including statements regarding future results of operations and financial position, business strategy, current and prospective product candidates, ongoing and planned clinical trials and preclinical activities, including the initiation, timing, enrollment, progress and results of our preclinical and clinical studies and our research and development programs, product approvals, research and development costs, current and prospective collaborations, the timing and likelihood of success of our Phase 1b/2a clinical trial of RTB101, alone or in combination with sirolimus, in Parkinson's disease and the timing or likelihood of regulatory progress, results, filings and approvals, expectations regarding market acceptance and size, plans and objectives

of management for future operations, and future results of anticipated product candidates, are forward-looking statements. New risks and uncertainties may emerge from time to time, and it is not possible to predict all risks and uncertainties. No representations or warranties (expressed or implied) are made about the accuracy of any such forward-looking

statements.

These statements are also subject to a number of material risks and uncertainties that are discussed in the section entitled "Risk Factors" in resTORbio's annual report on Form 10-K for the fiscal year ended December 31, 2018, as well as discussions of potential risks, uncertainties, and other important factors in resTORbio's subsequent filings with the Securities and Exchange Commission. Any forward-looking statement speaks only as of the date on which it was made. Neither we, nor our affiliates, advisors or representatives, undertake any obligation to publicly update or revise any forward-looking statement, whether as a result of new information, future events or otherwise, except as required by law.

Certain information contained in this presentation relates to or is based on studies, publications, surveys and other data obtained from third-party sources and the Company's own internal estimates and research. While we believe these third-party sources to be reliable as of the date of this presentation, we have not independently verified, and we make no representation as to the adequacy, fairness, accuracy or completeness of any information obtained from third-party sources. In addition, all of the market data included in this presentation involves a number of assumptions and limitations, and there can be no guarantee as to the accuracy or reliability of such assumptions. Finally, while we believe our own internal research is reliable, such research has not been verified by any independent source.

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resTORbio highlights

Extensive preclinical data demonstrate that TORC1 inhibition may ameliorate multiple aging related diseases, including neurodegenerative diseases

TORC1 inhibition may be a promising approach for the treatment of Parkinson's disease (PD)

• Ameliorateslevodopa-induced dyskinesia in preclinical PD models
• Induces lysosomal biogenesis and autophagy, clearsalpha-synuclein aggregates and is neuroprotective in preclinical PD models
• Lead candidate, RTB101, is an oral, selective and potent TORC1 inhibitor that has been observed in preclinical models to cross the blood brain barrier and induce autophagy in neurons

Ongoing Phase 1b/2a clinical trial of RTB101 +/- sirolimus for PD

• Safety, tolerability and cerebrospinal fluid (CSF) exposure data are expected bymid-2020 in PD patients
• RTB101 has the potential to alleviatelevodopa-induced dyskinesia and may offer the first opportunity to slow disease progression by inducing autophagy in the brain of PD patients
• In interim data from three cohorts in the Phase 1b/2a study we observed that RTB101 is well tolerated, crosses the blood brain barrier, and reaches concentrations in cerebrospinal fluid observed to inhibit the activity of TORC1 and induce autophagy in neuronal cells
  -Sirolimus at the dose of 2 mg, alone or in combination with RTB101, was not detected in the CSF

Cash, cash equivalents and marketable securities of $117.3 million as of September 30, 2019

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Pipeline

PROGRAM

CURRENT INDICATIONS*	RTB101 or
	RTB101 +
	sirolimus
POTENTIAL INDICATIONS**	RTB101 or
RTB101 +

RTB101 + rapalog

RTB101 or rapalog

INDICATION	DISCOVERY	PRECLINICAL	PHASE 1	PHASE 2	PHASE 3
Parkinson's Disease				P H A S E 1 B / 2 A
			O N G O I N G

Neurodegenerative

Diseases

Diseases associated with

TORC1 hyperactivation

• For Parkinson's disease, we may be required to file an investigational new drug application, or IND, with the U.S. Food and Drug Administration, prior to initiating Phase 2 clinical trials ** For neurodegenerative diseases and diseases associated with TORC1 hyperactivation, subject to review by the U.S. Food and Drug Administration, we believe we may
  have the ability to initiate Phase 2 clinical trials without the need to conduct additional Phase 1 trials.

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Broad TORC1 inhibition with RTB101 has the potential to ameliorate levodopa- induced dyskinesia and to be neuroprotective in Parkinson's disease patients

Decreased phosphorylation of S6K and 4EBP1 decrease protein synthesis and are

RTB101

TORC1

S6K

4EBP1

ULK1

TFEB

Activation of ULK1 and TFEB have been shown to promote autophagy and lysosomal

associated with amelioration of levodopa- induced

Decreased

Protein

Synthesis

SREBP

Increased Autophagy

biogenesis which are associated with neuroprotection in

Decreased

Increased

dyskinesia in preclinical PD models

Protein

Synthesis

Decreased

Lipid

Synthesis

Lysosomal Biogenesis

preclinical PD models

Nyfeler et al. Molecular and Cellular Biology, 2011; Nyfeler et al. PLoS ONE,2012; Eid et al. PNAS, 2017; Roczniak-Ferguson et al. Sci Signal, 2012; Santini et al. Sci Signaling, 2009

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Neurodegenerative Diseases

Parkinson's Disease: Disease modification

Protein aggregation is a common pathogenic mechanism in aging- related neurodegenerative diseases

Alzheimer's	Parkinson's	Huntington's
Disease	Disease	Disease

Amyloid β	Phosphorylated	α-synuclein	Mutated
protein	tau	huntingtin

Amyloid	Neurofibrillary	Lewy	Aggregated
plaques	tangles	bodies	huntingtin

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Parkinson's Disease

Prevalence

• Second most common neurodegenerative disease
• Affects 1% of population over 55 years of age in the U.S.

Pathology

• Accumulation of Lewy body protein aggregates containing a- synuclein and death of the neurons that produce the neurotransmitter dopamine in the substantia nigra

Clinical manifestations

• Four cardinal motor symptoms:
• • Resting tremor
  • Bradykinesia (slowed movement)
  • Muscle rigidity
  • Postural instability

Current therapies treat symptoms of PD but do not alter disease progression

• Levodopa is used to treat PD; however, its effect tends to wear off over time and can lead to disablinglevodopa-induced dyskinesia

Image from Wikiwand

Parkinson's

Disease

α-synuclein

Lewy bodies

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Defective autophagy may contribute to the accumulation of aggregated proteins in PD and other neurodegenerative diseases

Autophagy is a mechanism by which aggregated misfolded proteins and dysfunctional organelles are broken down and recycled in cells

Toxic protein	Phagophore	Autophagosome	Autophagolysosome
Aggregate

Lysosome

Neuroprotection

Menzies et al. Neuron, 2017

9

Mutations in autophagy-related proteins are found in PD and other neurodegenerative diseases suggesting that deficient autophagy contributes to neurodegenerative disease pathogenesis

Menzies et al. Neuron, 2017

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TORC1 inhibitors have the potential to be disease modifying in neurodegenerative diseases by upregulating autophagy and lysosomal biogenesis

Toxic protein	Phagophore	Autophagosome	Autophagolysosome
Aggregate

TORC1

inhibition

P

Increased

ULK1phagophoreLysosomeformation

P	TFEB	Increased
	TFEB	Lysosomal
	Nucleus	Biogenesis

Neuroprotection

Menzies et al. Neuron, 2017; Roczniak-Ferguson et al. Sci Signal, 2012; Nyfeler et al. Molecular and Cellular Biology, 2011

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TORC1 inhibition is neuroprotective in PD pre-clinical models

	Increased TFEB	Clearance of toxic	Improved			Improved
		nuclear	Neuronal			Motor
		a-syn aggregates
	translocation	Survival			Performance
			C.			D.
	A.		B.

*p < 0.05 compared with the 3-wkα-syn group #p < 0.05 compared with α-syn+vehicle group

In a rat PD model that overexpresses a-syn in the substantia nigra, the TORC1 inhibitor CCI-779 started 3 weeks after adenoviral delivery of a-syn (3w) and given every other day for 5 weeks was shown (A)to correct impaired TFEB function (as reflected by increased TFEB nuclear translocation), (B)decreased striatal a-syn levels (both monomeric and high molecular weight (HMW) aggregates), (C)increased dopaminergic neuron survival and (D)improved motor function.

Decressac et al. PNAS, 2013

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TORC1 inhibitors under evaluation in a Phase 1b/2a trial in Parkinson's disease

sirolimus (rapamycin):

• Allosteric inhibitor of TORC1
• Partial TORC1 inhibitor: only consistently inhibits S6K downstream of TORC1
• Approved for use in humans

RTB101:

• ATP competitive catalytic site inhibitor of mTOR protein kinase
• Consistently inhibits phosphorylation of all targets downstream of TORC1
• Crosses the blood brain barrier in animal models
• Tested in >1,000 humans
• Human maximum tolerated dose: 1,200 mg/day

sirolimus

(rapamycin)

RTB101

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Potential spectrum of TORC1 inhibition with RTB101 and sirolimus

High Concentration of RTB101 or Low Concentrations of RTB101+ sirolimus

sirolimus

TORC1

S6K

ULK1

4EBP1TFEB

	TORC1
S6K	ULK1
4EBP1	TFEB
	SREBP

Targets for neuroprotection

Decreased

Protein

Synthesis

SREBP

Decreased	Increased
Protein
Synthesis	Autophagy

DecreasedIncreased

ProteinLysosomal

SynthesisBiogenesis

Decreased

Lipid

Synthesis

in PD

Indicates consistent inhibition of target phosphorylation

Nyfeler et al. Molecular and Cellular Biology, 2011; Nyfeler et al. PLoS ONE,2012; Eid et al. PNAS, 2017; Roczniak-Ferguson et al. Sci Signal, 2012

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The combination of RTB101 and sirolimus synergize to inhibit TORC1 and may lower the RTB101 brain exposure required to induce autophagy

SK-N-SH neuroblastoma cells were exposed to increasing concentrations of RTB101 (y axis) and/or increasing concentrations of sirolimus (x axis). Orange shaded areas indicate concentrations of RTB101 and/or sirolimus that induce >50% maximal autophagy activation. Autophagocytic flux was measured using an mCherry- GFP-LC3 cell- based assay

Total Free (5%)

		87.50	4.38	130.58	114.37	156.80	170.61	173.28	181.56	196.15	174.61	158.67	216.07
		43.75	2.19	91.48	71.47	123.06	118.25	166.88	154.73	189.63	194.12	190.70	214.89
		21.88	1.09	31.89	25.16	81.50	100.98	125.12	137.82	212.58	197.37	166.87	218.33
		10.94	0.55	0.02	4.25	29.25	41.45	88.97	138.95	155.32	184.65	146.93	179.15
% maximal	(nM)	5.47	0.27	-12.14	-14.12	-1.11	8.36	44.22	81.09	103.23	143.72	120.56	123.57
activation of
autophagy	RTB101	2.	0.14	-12.10	-6.71	-0.19	-1.19	25.53	43.99	75.14	96.76	73.48	100.10
	1	0.07	-7.40	-17.37	0.03	0.09	13.03	29.69	41.98	54.65	60.23	68.35
		68	0.03	-23.25	-25.36	3.41	-2.42	5.87	16.31	26.84	52.55	33.51	31.80
		0.34	0.02	-16.81	-28.70	-7.67	-5.83	5.18	14.95	9.42	33.10	21.35	43.68
		0	0	-11.63	-20.72	-6.80	-6.46	-1.54	9.74	2.82	13.34	10.25	-4.02
			Free (2.5%)	0	0.000053 0.000214 0.000854 0.003418 0.013672 0.054688 0.218750 0.875000	3.5
			Total	0	0.002136 0.008545 0.034180 0.136719 0.546875 2.187500	8.75	35.00	140.00
							sirolimus (nM)

RTB101 300 mg monotherapy cerebrospinal fluid concentration

observed in PD patients

15

Neurodegenerative Diseases

Parkinson's Disease: Levodopa-induced dyskinesia

Advantage of PD as a clinical indication for TORC1 inhibitors: levodopa- induced dyskinesia (LID) is a potential clinical endpoint that can be assessed in a shorter time frame than disease progression

• LID is a disabling side effect of chronic levodopa treatment associated with significantly impaired quality of life and increased health care costs1
• Most common dyskinesias:
• • chorea (jerky involuntary movements, especially around the face, shoulders, and hips)
  • dystonia (involuntary muscle contraction leading to twisting, repetitive movements, or abnormal posture in affected muscle or muscle group)
• Average time to onset of dyskinesia estimated at 6.5 years1
• > 90% of PD patients will have LID after 15 years of levodopa therapy3

1and figure Calabresi et al., 2010; 2Tran et al., 2018; 3Ahlskog and Muenter 2001 and Hely et al2005

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Multiple pathways implicated in levodopa-induced dyskinesia (LID) pathogenesis converge on ERK and downstream TORC1 hyperactivation

TSC

Medium Spiny Neuron
TORC1	4EBP1	Dyskinesia
S6K

Adapted from Calabrisi P et al., Lancet Neurol, 2010 Santini et al. Sci Signaling, 2009

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TORC1 is hyperactivated in medium spiny neurons in preclinical PD models of LID and TORC1 inhibition alleviates LID

A		B
	TORC1 Activation (pS6 levels)

Control mice treated with L-DOPA

PD Mice treated with L-DOPA

PD Mice treated with L-DOPA+rapamycin 2mg/kg

A: Administration of levodopa in a mouse model of PD (unilateral 6- OHDA lesion) led to hyperactivation of TORC1(as assessed by pS6 levels) in medium spiny neurons and development of dyskinesia.

B: Rapamycin inhibited TORC1 activation and ameliorates dyskinesia, as assessed by an abnormal involuntary movement score (AIMs), determined by an observer blind to treatment assignment. ooo,*** P<0.001 versus untreated control.

PD Mice treated with L-DOPA+rapamycin 5 mg/kg

Santini et al. Sci Signaling, 2009

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resTORbio Phase 1b/2a Parkinson's disease trial

Randomized, Placebo-Controlled

Phase 1b/2a Study (4-week dosing)

Design	•	Mild-moderate PD patients (mH&Y I-III)
	•On standard of care PD drugs
	•	Once weekly dosing

Study SizeN=45 (2:1 randomization)

Primary endpoint:

• Safety and tolerability

Secondary endpoint:

Key Endpoints•Exposure in blood, plasma and CSF

Exploratory endpoints:

• Biomarkers in plasma and CSF
• Clinical assessments, wearables

Cohort	RTB 101	sirolimus
dose	dose
	(mg)	(mg)
1	300	0
2	0	2		or
3	300	2
	matching
				placebo
4	300	4
5	300	6

• Study initiated in 1Q19
• Data expected bymid-2020

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RTB101 CSF Concentrations in 6 PD patients dosed with RTB101 300 mg once weekly

		CSF RTB101 (nM)
		4h post Dose 4
4.50
4.00
3.50
3.00
2.50
2.00
1.50
1.00
0.50
0.00
101-004	101-901	102-001	103-001	103-003	103-006

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The combination of RTB101 and sirolimus synergize to inhibit TORC1 and may
lower the RTB101 brain exposure predicted to be required for clinical benefit
in PD			Total	Free (5%)
		87.50	4.38	100	99	104	99	101	104	102	101	105	99
			43.75	2.19	97	101	100	102	95	102	104	104	102	103
			21.88	09	84	86	99	98	100	101	104	102	99	104
	% maximal		10.94	.55	51	62	79	99	102	104	103	104	105	104
SK-N-SH	Inhibition of		5.47	0.27	26	38	54	91	98	104	103	103	105	104
	2.73	0.14	12	30	39	74	97	102	103	104	104	104
neuroblastoma cells	pS6K		1.37	0.07	8	18	27	56	89	101	103	103	104	102
were exposed to			0.68	0.03	14	12	30	49	85	101	103	105	103	104
increasing			0.34	0.02	6	7	21	49	79	100	104	104	105	103	Target inhibition for
		0	0	6	12	16	45	73	98	103	103	104	103
concentrations of
RTB101 (y axis)				Free (5%)											levodopa-induced
and/or increasing			87	4.38	55	57	65	73	79	87	93	97	99	96	dyskinesia
concentrations of			75	2.19	25	33	39	54	65	72	83	71	77	89
		.88	1.09	5	16	13	28	38	62	62	68	62	76
sirolimus (x axis).	% maximal
(nM)	.94	0.55	-6	-7	-7	0	13	28	36	40	45	51
Orange shaded areas	Inhibition of	.47	0.27	-7	-12	-21	-44	-8	6	13	12	25	30
indicate	p4EBP1	2.73	0.14	-12	-10	-8	-10	-12	-2	-6	1	9	18
RTB101	1.	0.07	-9	-10	-10	-22	-25	-9	-4	-3	6	5
concentrations of		0.	0.03	-7	-6	-4	-16	-33	-10	-6	-3	5	4
RTB101 and/or
		0.02	-17	-15	-11	-21	-31	-17	-9	-10	9	0
sirolimus that induce		0	0	-16	-15	-8	-13	-25	-11	-9	-10	1	-3
>50% maximal S6K or
4EBP1			87.50	Free (5%)	130.58	114.37	156.80	170.61	173.28	181.56	196.15	174.61	158.67	216.07
phosphorylation			4.38
% maximal		43.75	2.19	91.48	71.47	123.06	118.25	166.88	154.73	189.63	194.12	190.70	214.89
inhibition or >50%
	21.88	1.09	31.89	25.16	81.50	100.98	125.12	137.82	212.58	197.37	166.87	218.33
maximal autophagy	activation of		10.	0.55	0.02	4.25	29.25	41.45	88.97	138.95	155.32	184.65	146.93	179.15	Target inhibition for
activation			2.73	0.27	-12.14	-14.12	-1.11	8.36	44.22	81.09	103.23	143.72	120.56	123.57
			0.14	-12.10	-6.71	-0.19	-1.19	25.53	43.99	75.14	96.76	73.48	100.10	neuroprotection and
			1.37	0.07	-7.40	-17.37	0.03	0.09	13.03	29.69	41.98	54.65	60.23	68.35
			0.68	0.03	-23.25	-25.36	3.41	-2.42	5.87	16.31	26.84	52.55	33.51	31.80	disease modification
			0.34	0.02	-16.81	-28.70	-7.67	-5.83	5.18	14.95	9.42	33.10	21.35	43.68
			0	0	-11.63	-20.72	-6.80	-6.46	-1.54	9.74	2.82	13.34	10.25	-4.02
RTB101 300 mg			Free
cerebrospinal fluid concentration		(2.5%)	0	0.000053	0.000214	0.000854 0.003418 0.013672 0.054688 0.218750 0.875000	3.5
observed in PD patients			Total	0	0.002136	0.008545	0.034180	0.136719	0.546875	2.187500	8.75	35.00	140.00
													22
									sirolimus (nM)

Neurodegenerative Diseases

Huntington's disease

Induction of autophagy with TORC1 inhibitors may have potential benefit in multiple neurodegenerative diseases in which protein aggregation contributes to disease pathogenesis

Alzheimer's	Parkinson's	Huntington's
Disease	Disease	Disease

Amyloid β	Phosphorylated	α-synuclein	Mutated
protein	tau	huntingtin

Amyloid	Neurofibrillary	Lewy	Aggregated
plaques	tangles	bodies	huntingtin

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In a preclinical model of Huntington's disease, the combination of RTB101 and everolimus (an analog of sirolimus) cleared protein aggregates and

was neuroprotective

Aggregated mHtt protein levels in cultured cortico- striatal slices from R6/2 Huntington's disease mouse.

250nM 50nMevero RTB101evero RTB101

RTB101

Drug concentrations in the figures are total concentrations

250 nM everolimus	50 nM RTB101	300 nM RTB101

250 nM everolimus		250 nM everolimus	250 nM everolimus
+ 10 nM RTB101		+ 30 nM RTB101	+ 50 nM RTB101

Neurofilament is a	DARPP-32 is a marker
marker of axons	of cell soma

Source: Novartis Data on file

25

resTORbio highlights

Extensive preclinical data demonstrate that TORC1 inhibition may ameliorate multiple aging related diseases, including neurodegenerative diseases

TORC1 inhibition may be a promising approach for the treatment of Parkinson's disease (PD)

• Ameliorateslevodopa-induced dyskinesia in preclinical PD models
• Induces lysosomal biogenesis and autophagy, clearsalpha-synuclein aggregates and is neuroprotective in preclinical PD models
• Lead candidate, RTB101, is an oral, selective and potent TORC1 inhibitor that has been observed in preclinical models to cross the blood brain barrier and induce autophagy in neurons

Ongoing Phase 1b/2a clinical trial of RTB101 +/- sirolimus for PD

• Safety, tolerability and cerebrospinal fluid (CSF) exposure data are expected bymid-2020 in PD patients
• RTB101 has the potential to alleviatelevodopa-induced dyskinesia and may offer the first opportunity to slow disease progression by inducing autophagy in the brain of PD patients
• In interim data from three cohorts in the Phase 1b/2a study we observed that RTB101 is well tolerated, crosses the blood brain barrier, and reaches concentrations in cerebrospinal fluid observed to inhibit the activity of TORC1 and induce autophagy in neuronal cells
  -Sirolimus at the dose of 2 mg, alone or in combination with RTB101, was not detected in the CSF

Cash, cash equivalents and marketable securities of $117.3 million as of September 30, 2019

26

Targeting the biology of aging to treat aging-related diseases

Corporate Presentation

February 2020