COMPASS Pathways : Presentation – March 2024

Transforming Mental Health Care

Investor Presentation

March2024

Disclaimer

Cautionary Note Regarding Forward-LookingStatements This presentation includes "forward-looking statements" within the meaning of the Private Securities

Litigation Reform Act of 1995, as amended. In some cases, you can identify forward-looking statements by terms such as "believe," "continue," "could," "estimate," "expect," "may," "might," "plan," "potential," "project," "should," "target," "will," "would," or the negative of these terms, and similar expressions intended to identify forward-looking statements. However, not all forward-looking statements contain these identifying words. These forward-looking statements include express or implied statements relating to our strategic plans or objectives; our expectations and projections about our future cash needs

and financial results, the anticipated proceeds to be received from the pending exercise of warrants issued in the private placement and future exercises, if any, of remaining warrants issued in the private placement; our expectations for our phase 3 program in treatment resistant depression, including the expected timing for any data readouts, and the potential for that or other trials to support regulatory filings and approvals; our expectations regarding timing for our phase 2 trial in post traumatic stress disorder, including the expected timing for any data readouts; our expectations regarding the future reimbursement and accessibility of COMP360 psilocybin therapy, if FDA approval is obtained, including the potential impact of the CPT III codes

on such reimbursement and accessibility; our ability to launch and successfully commercialize COMP360 psilocybin therapy; and our ability to advance COMP360 psilocybin therapy in other areas of high unmet mental health need and to discover and advance new drug compounds. By their nature, these statements are subject to numerous risk and uncertainties, including the our need for substantial additional funding to achieve our business goals, including to repay the term loan facility, and if we are unable to obtain this funding when needed and on acceptable terms, we could be forced to delay, limit or terminate our clinical development efforts; the risk that the pending warrant exercises for approximately $9.0 million in proceeds will not settle; clinical development is lengthy and outcomes are uncertain, and therefore our phase 3 clinical trials in TRD and our other clinical trials may be delayed or terminated; impact of global macroeconomic trends on our business, our expectations about the outcomes of our clinical programs, actions of regulatory agencies, our dependence on third parties in connection with our clinical trials and other factors beyond our control, that could cause our actual results, performance or achievements to differ materially and adversely from those anticipated or implied in our statements. For additional disclosure regarding these and other risks we may face, see the disclosure contained under the heading "Risk Factors" and elsewhere in the Company's most recent Annual Report on Form 10-K, Quarterly Report on Form 10-Q and subsequent public filings with the US Securities and Exchange Commission (the "SEC"). You should not rely upon forward-looking statements as predictions of future events. Although our management believes that the expectations reflected in our statements are reasonable, we cannot guarantee that the future results, levels of activity, performance or events and circumstances described in the forward-looking statements will be achieved or occur. Moreover, neither we, nor any other person, assumes responsibility for the accuracy and completeness of these statements. Accordingly, you are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date such statements are made and should not be construed as statements of fact. Except as required by applicable law, we undertake no obligation to update these forward-looking statements to reflect any new information, events or circumstances after the date hereof, or to reflect the occurrence of unanticipated events. No representations or warranties (expressed or implied) are made about the accuracy of any such forward-looking statements.

Market & Industry Data Projections, estimates, industry data and information contained in this presentation, including our general expectations about our market position and market opportunity, are based on information from third-party sources, publicly available information, our knowledge of our industry and assumptions based on such information and knowledge. Although we believe that our third party-sources are reliable, we cannot guarantee the accuracy or completeness of our sources. All of the projections, estimates, market data and industry information used in this presentation involve a number of assumptions and limitations, and you are cautioned not to give undue weight to such information. In addition, projections, estimates and assumptions relating to our and our industry's future performance are necessarily subject to a high degree of uncertainty and risk due to a variety of factors, including, but not limited to, those described above, that could cause future performance to differ materially from our expressed projections, estimates and assumptions or those provided by third parties.

This presentation shall not constitute an offer to sell or the solicitation of an offer to buy securities, nor shall there be any sale of securities in any state or jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state or jurisdiction.

2 | © CompassPathways

We're a biotechnology company …

• dedicatedtoacceleratingpatientaccesstoevidence-based
  innovationinmentalhealth.

3 | © CompassPathways

COMP360 psilocybin treatment includes three elements

COMP360 psilocybin treatment

COMP360 psilocybin

Our synthetic, high-purity polymorphic crystalline formulation of psilocybin, a psychoactive compound.

Psychological support

Psychological support from registered and trained mental health professionals.

Digital tools

A patient app, therapist portal and AI-driven analytics platform enhancing patient experience and outcomes.

4 | © CompassPathways

TRD treatment pathway: significant unmet need for 100 million patients

Treatment pathway stage

Line of therapy

Estimated number of patients (worldwide)

Available treatments

% relapse

New onset depression	Persistent depression	Treatment-resistant
Major depressive disorder	Major depressive disorder
depression (TRD)
(MDD)	(MDD)
	First line		Second line		Third line +
					100 million (~1 in 3 of total)
	320 million		200 million	US health care cost approx. $17-
					25k per patient/year
				-	Antidepressants
				-	Augmentation therapy
					(antidepressants, mood
		-	Antidepressants		stabilizers, anticonvulsants,
-	Antidepressants		atypical antipsychotics,
-	Antidepressant combinations
-	Psychological interventions,		esketamine)
-	Psychological interventions
	e.g., CBT*	-	Ketamine
				- Somatic therapy (rTMS, tDCS,
					ECT, DBS)*
				-	High-intensity psychological
					interventions
	60-70%		50-75%		80-90%

*NOTE: CBT = cognitive behavioural therapy; rTMS = repetitive transcranial magnetic stimulation; tDCS=transcranial direct current stimulation; ECT=electroconvulsive therapy; DBS=deep brain stimulation SOURCE Table adapted from Rush, A. J., Trivedi, M. H., Wisniewski, S. R., Nierenberg, A. A., Stewart, J. W., Warden, D., ... & Fava, M. (2006). Acute and longer-term outcomes in depressed outpatients requiring one or several treatment steps: a STAR* D report. American Journal of Psychiatry, 163(11), 1905-1917; Zhdanava M, Pilon D, Ghelerter I, et al. The prevalence and national burden of treatment-resistant depression and major depressive disorder in the United States. J Clin Psychiatry. 2021;82(2):20m13699.

5 | © CompassPathways

COMP001 phase 2b study design and primary endpoint (n=233)

3-6 weeks	Day 1	Day 2	Week 1	Week 2	Week 3	Week 12

	D-1: Baseline	D1: COMP360
Screening	psilocybin	Day 2	Week 1	Week 2	Week 3		Week 12
(V1)	(V2)	administration	(V4)	(V5)	(V6)	(V7)		(EOS., V10)
		(V3)
Weekly visits (V1a, V1b,						Week 6	Week 9
etc) for antidepressant						(V8)	(V9)
	discontinuation (if						Remote	Remote
	required) and						visit	visit
	preparation visits

1mg COMP360	10mg COMP360	25mg COMP360	Primary endpoint
79 participants	75 participants	79 participants	Reduction of symptoms of depression as
			measured by change in MADRS total score
			from baseline to week 3

RANDOMISATION 1:1:1

Note: MADRS = Montgomery-Åsberg Depression Rating Scale; EOS = end of study; TRD = treatment-resistant depression; D = day; V = visit

6 | © CompassPathways

Phase 2b trial: Results demonstrate the potential for a rapid, sustained response in TRD

Published in The NEW ENGLAND JOURNAL of MEDICINE

In a randomized, controlled, double- blind trial, three groups of participants were given a single dose (either 1mg, 10mg or 25 mg) of COMP360 psilocybin alongside psychological support.

Results were measured as a change on the MADRS* depression scale from baseline (a day prior to administration) over a 12-week period.

The primary endpoint of this study was the change from baseline in MADRS total score at week 3.

Primary efficacy assessment,		Follow-up period,
3 weeks post administration		3-12 weeks post administration

1 mg

10 mg

25 mg

Difference vs 1 mg at Week 3

• 25 mg: -6.6 (95% confidence interval: -10.2 ; -2.9),p<0.001
• 10 mg: -2.5, p=0.184

Efficacy: We saw a	Rapid onset of action:
statistically significant and	The effect occurred the
clinically meaningful	day after the
reduction in depression	administration.
symptoms.

Durability: We saw a sustained response at week 12 - a positive indication for high potential as a monotherapy.

7 | © CompassPathways

NOTE: *Least square mean change from baseline in MADRS total score; MADRS = Montgomery-Åsberg Depression Rating Scale

Phase 2b trial: Those participants who showed a sustained response also showed signs of improvement beyond the reduction of depression symptoms

Sustained responders are

participants who responded (≥50% change in MADRS total score from baseline) at weeks 3 and 12, and at least one visit out of week 6 and 9, and who did not start new treatments for depression.

Sustained non-responders are participants who did not respond (<25% change in MADRS total score from baseline) at weeks 3 and 12, and at least one visit out of week 6 or 9.

Sustained responders (n=19)

Sustained non-responders (n=21)

Quality of life: Sustained responders were found	Positive affect: Sustained responders were
to have a clinically meaningful increase in quality	found to have a clinically meaningful increase
of life from baseline at week 3 and week 12 with	in positive affect from baseline on the day
scores in the normal range after treatment	after the psilocybin session and at week 3

NOTE: EQ-5D-3L= EuroQoL 5-Dimensions3-Levels; PANAS= Positive and Negative Affect Schedule; SD= standard deviation

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Phase 2b trial: COMP360 psilocybin treatment was generally well-tolerated

Treatment-emergent adverse events (TEAEs)

>90% of TEAEs were of mild or moderate severity.

most frequent TEAEs

5 across the 10mg and 25mg doses were headaches, nausea, fatigue, insomnia and anxiety.

of TEAEs occurring on the

>77% day of administration resolved on the same or next day; most were mild or moderate.

9 | © CompassPathways

There were no concerns with vital signs, ECG or clinical laboratory data in any of the treatment groups

TEAEs involving hallucinations (which only occurred in the 25mg and 10mg groups) and illusions (all groups) started and resolved on the day of administration.

TESAEs of suicidal ideation, suicidal behaviour and intentional self-injury were uncommon but occurred unevenly across groups in non-responders (see Appendix for additional information)

• All patients who experienced these events during the trial had said during screening that they had had suicidal thoughts prior to the trial.
• The majority of these TESAEs. (10 of 14) occurred at least one week after administration of COMP360 psilocybin treatment and all suicidal behaviours occurred at least one

month after administration

Phase 3 program: Overview of ongoing pivotal trial designs

Pivotal trial 1 Single dose

Week 6 (Part A)

Primary endpoint*

COMP360

25 mgLong- term

Randomisation = 2:1

n = 255

(170:85)

monotherapy

(COMP 005)

Placebo

follow-up

Top line data expected fourth

quarter 2024

Pivotal trial 2 Fixed repeat dose monotherapy (COMP 006)

Week 6 (Part A)

	Week 3 Primary endpoint*
COMP360	COMP360
25 mg	25 mg
COMP360	COMP360	Long-
term
10 mg	10 mg
follow-up
COMP 360	COMP360
1 mg	1 mg

Randomisation = 2:1:1

n = 568 (284:142:142)

Top line data expected mid 2025

The phase 3 program will be conducted across approx. 150 sites in 12 countries. Key secondary endpoints include change in MADRS at week 9, 6 weeks following second dose. The participant population (TRD definition and core inclusion/exclusion criteria) remains unchanged compared to Phase 2b

*Primary endpoint - change from baseline in MADRS total score at Week 6

10 | © CompassPathways