The Securities and Exchange Commission has not necessarily reviewed the information in this filing and has not determined if it is accurate and complete.
The reader should not assume that the information is accurate and complete.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
FORM 13F

FORM 13F COVER PAGE

OMB APPROVAL
OMB Number: 3235-0006
Expires: July 31, 2015
Estimated average burden
hours per response: 23.8

Report for the Calendar Year or Quarter Ended: 03-31-2022
Check here if Amendment   Amendment Number:
This Amendment (Check only one.):   is a restatement.
  adds new holdings entries.
Institutional Investment Manager Filing this Report:
Name: Palo Alto Investors LP
Address: 470 UNIVERSITY AVE
PALO ALTO , CA94301
Form 13F File Number: 028-11013

The institutional investment manager filing this report and the person by whom it is signed hereby represent that the person signing the report is authorized to submit it, that all information contained herein is true, correct and complete, and that it is understood that all required items, statements, schedules, lists, and tables, are considered integral parts of this form.

Person Signing this Report on Behalf of Reporting Manager:
Name: Angela Nguyen-Dinh
Title: Chief Compliance Officer
Phone: (650) 325-0772
Signature, Place, and Date of Signing:
Angela Nguyen-Dinh Palo Alto , CA 05-16-2022
[Signature] [City, State] [Date]
Report Type (Check only one.):
X 13F HOLDINGS REPORT. (Check here if all holdings of this reporting manager are reported in this report.)
  13F NOTICE. (Check here if no holdings reported are in this report, and all holdings are reported by other reporting manager(s).)
  13F COMBINATION REPORT. (Check here if a portion of the holdings for this reporting manager are reported in this report and a portion are reported by other reporting manager(s).)
Form 13F Summary Page
Report Summary:
Number of Other Included Managers: 0
Form 13F Information Table Entry Total: 35
Form 13F Information Table Value Total: 1,293,496
(thousands)
List of Other Managers Reporting for this Manager:
[If there are no entries in this list, omit this section.]
Form 13F File Number Name

List of Other Included Managers:
Provide a numbered list of the name(s) and Form 13F file number(s) of all institutional investment managers with respect to which this report is filed, other than the manager filing this report.
[If there are no entries in this list, state “NONE” and omit the column headings and list entries.]
No. Form 13F File Number Name


SEC FORM 13F-HR

The Securities and Exchange Commission has not necessarily reviewed the information in this filing and has not determined if it is accurate and complete.
The reader should not assume that the information is accurate and complete.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
FORM 13F

FORM 13F INFORMATION TABLE

OMB APPROVAL
OMB Number: 3235-0006
Expires: July 31, 2015
Estimated average burden
hours per response: 23.8

COLUMN 1 COLUMN 2 COLUMN 3 COLUMN 4 COLUMN 5 COLUMN 6 COLUMN 7 COLUMN 8
VALUE SHRS OR SH/ PUT/ INVESTMENT OTHER VOTING AUTHORITY
NAME OF ISSUER TITLE OF CLASS CUSIP (x$1000) PRN AMT PRN CALL DISCRETION MANAGER SOLE SHARED NONE
ABIOMED INC COM 003654100 163,764 494,397 SH SOLE 494,397 0 0
ACADIA PHARMACEUTICALS INC COM 004225108 54,539 2,251,834 SH SOLE 2,251,834 0 0
ALDEYRA THERAPEUTICS INC COM 01438T106 715 160,800 SH SOLE 160,800 0 0
ALIGN TECHNOLOGY INC COM 016255101 19,317 44,305 SH SOLE 44,305 0 0
ALIMERA SCIENCES INC COM 016259202 1,125 200,919 SH SOLE 200,919 0 0
ALKERMES PLC COM G01767105 17,722 673,571 SH SOLE 673,571 0 0
AMICUS THERAPEUTICS INC COM 03152W109 93,789 9,903,761 SH SOLE 9,903,761 0 0
ANAPTYSBIO INC COM 032724106 10,664 431,024 SH SOLE 431,024 0 0
BIOGEN INC COM 09062X103 76,023 360,981 SH SOLE 360,981 0 0
BIOMARIN PHARMACEUTICAL INC COM 09061G101 164,964 2,139,614 SH SOLE 2,139,614 0 0
CLOVIS ONCOLOGY INC COM 189464100 9,037 4,473,967 SH SOLE 4,473,967 0 0
CYTOKINETICS INC COM 23282W605 4,112 111,717 SH SOLE 111,717 0 0
EHEALTH INC COM 28238P109 20,505 1,652,260 SH SOLE 1,652,260 0 0
EPIZYME INC COM 29428V104 7,791 6,774,541 SH SOLE 6,774,541 0 0
GOSSAMER BIO INC COM 38341P102 15,249 1,756,757 SH SOLE 1,756,757 0 0
GRITSTONE ONCOLOGY INC COM 39868T105 9,602 2,330,504 SH SOLE 2,330,504 0 0
INSMED INC COM 457669307 138,211 5,881,299 SH SOLE 5,881,299 0 0
KALEIDO BIOSCIENCES INC COM 483347100 511 309,692 SH SOLE 309,692 0 0
KARYOPHARM THERAPEUTICS INC COM 48576U106 41,431 5,621,533 SH SOLE 5,621,533 0 0
KEZAR LIFE SCIENCES INC COM 49372L100 10,906 656,200 SH SOLE 656,200 0 0
MAGENTA THERAPEUTICS INC COM 55910K108 1,254 432,300 SH SOLE 432,300 0 0
MARINUS PHARMACEUTICALS INC COM 56854Q200 293 31,330 SH SOLE 31,330 0 0
MIRUM PHARMACEUTICALS INC COM 604749101 1,425 64,700 SH SOLE 64,700 0 0
NOVAVAX INC COM 670002401 921 12,500 SH SOLE 12,500 0 0
PROTHENA CORP PLC COM G72800108 61,492 1,681,477 SH SOLE 1,681,477 0 0
REVANCE THERAPEUTICS INC COM 761330109 86,106 4,415,689 SH SOLE 4,415,689 0 0
RIGEL PHARMACEUTICALS INC COM 766559603 1,951 652,395 SH SOLE 652,395 0 0
SAGE THERAPEUTICS INC COM 78667J108 28,192 851,719 SH SOLE 851,719 0 0
STAAR SURGICAL CO COM 852312305 90,855 1,136,968 SH SOLE 1,136,968 0 0
SYNDAX PHARMACEUTICALS INC COM 87164F105 10,647 612,600 SH SOLE 612,600 0 0
TACTILE SYSTEMS TECHNOLOGY I COM 87357P100 546 27,100 SH SOLE 27,100 0 0
TRAVERE THERAPEUTICS INC COM 89422G107 4,280 166,069 SH SOLE 166,069 0 0
UNITED THERAPEUTICS CORP COM 91307C102 117,169 653,079 SH SOLE 653,079 0 0
UROGEN PHARMA LTD COM M96088105 213 24,500 SH SOLE 24,500 0 0
VANDA PHARMACEUTICALS INC COM 921659108 28,175 2,491,200 SH SOLE 2,491,200 0 0